ISLUSB-RTC-EV1ZMB - Intersil

Real Time Clock USB Evaluation System

Introduction

This evaluation system is a hardware and software platform

for testing Intersil Real Time Clock (RTC) devices, and the

system requires only a PC for the controller and power

functions. Intersil offers a large portfolio of RTC devices, with

features including a crystal oscillator, clock and date counters,

auto switch-over to battery backup, voltage monitoring with

low voltage reset, a watchdog timer, and alarms. The

ISL1209/19/21/32 devices include an event-detection

feature, and all but the ISL1209 include a time stamp function

for recording the time of the event. The ISL12022 features an

on-chip temperature sensor and temperature compensation,

while the ISL12020M/22M/22MA devices are RTC modules

with internal crystals. These module versions are factory

calibrated to account for crystal variability, and the on-chip

temperature sensor enables automatic crystal temperature

compensation, for the best RTC accuracy over temperature.

The evaluation system enables users to test all of these

functions, and to evaluate device performance criteria, such as

long-term clock accuracy. Hardware options, such as battery

and crystal types, can also be tested. The software sets up

easily, and enables evaluation of all major RTC functions. The

hardware’s two-piece construction - utilizing a motherboard

and a daughterboard - allows the evaluation of multiple RTC

products simply by switching out small daughterboards.

Operation and Overview of the

RTC Evaluation Board

Connections

The evaluation board consists of a motherboard and

daughterboard which connect together via J1 and J2. The

hardware uses a USB connection to communicate with the PC

loaded software, and USB drivers must be installed on the PC.

The provided USB cable, with type A and B connectors, is

required to hook up the board to a PC. The cable should be

connected to the PC first and then to the evaluation board.

Once connected, you will hear the USB “enumeration” tone,

and the motherboard “POWER” LED illuminates, indicating

that the USB connection is providing the +5V power.

Powering Down

The motherboard contains backup power sources, either a

supercap or an optional battery, so the RTC might operate off a

backup source when VDD powers down. If the user wishes to

totally power down the RTC device (e.g., a hard reset), either

disconnect the daughterboard from the motherboard or

connect motherboard jumper J4 to the “GND” position to

eliminate the backup sources. There is a 0.1µF VDD decoupling

capacitor on the daughterboard, which must discharge fully

before the RTC device stops operating. This discharge time can

be up to one second when using a VDD of 5V. Note that when

powered down, the RTC board cannot be monitored by the RTC

evaluation software.

Installing the RTC Software and USB Drivers

• Note: If you have previously loaded the Intersil RTC

evaluation software on the PC, you need to uninstall the

previously loaded version of the Intersil RTC Evaluation

software on the PC, Navigate to the uninstall program “All

Programs > Intersil > RTC_EVAL > RTC_uninstall” and run it.

If the uninstall program did not delete the old desktop

shortcut (right click on icon, then “delete”). Last you need to

uninstall the USB drivers before running the following install.

Go to Device Manager, (Control Panel, System, Hardware)

with the Eval board plugged in. Locate the “USBXpress

Device” under the “Universal Serial Bus controllers” branch

and then right click and select the “Uninstall”.

• Download the appropriate Installation program from the

Web. The same installation file is used for all Intersil RTC

Products, but changes for the Windows Version your

computer is running. The basic link to these installers is:

http://www.intersil.com/content/dam/Intersil/documents/

rtc_/ (add Web File name from below) or go to the products

main page and select the “Documents” tab.

• For Windows 2000 the Web File name is

“RTC_EVAL_Installer_w2k_V405.exe”

• For Windows XP & WIN7 the Web File name is

“RTC_EVAL_Installer_V405.exe”

• For Windows 8, the Web File name is

“RTC_EVAL_Installer_Win8_V405.exe”

• WIN8 Note: Before running the WIN8 installer there is a pre-

installation document on the Web that must be followed.

File name is

RTC_WIN8_Preinstallation_Procedure_081613.PDF.

Download this file, open it and follow the procedure.

• Do not plug in the RTC USB evaluation board yet.

• Double click on “RTC_EVAL_Installer...”.

•Click “Next”.

• If you agree with the license conditions, click “I accept” in

the license window, then click “Next” to install.

• Select a “Destination Location”, and click “Next”.

• Select a “Start Menu Folder”, and click “Next”.

• Click on “Create a Desktop Icon” and click “Next”.

Intersil RTC Devices Supported

WITH USER EEPROM NO USER EEPROM

ISL12024 ISL1208 ISL12020M

ISL12025 ISL12008 ISL12022M

ISL12026/26A ISL1209 ISL12022MA

ISL12027/27A ISL1218 ISL12032

ISL12028/28A ISL1219 ISL12057

ISL12029/29A ISL1220 ISL12058

ISL1221 ISL12059

ISL12022 ISL12082

Application Note 1745

October 9, 2013

AN1745.2

CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.

Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.

All other trademarks mentioned are the property of their respective owners.

Application Note 1745

2AN1745.2

October 9, 2013

• Click “Install” (you might get an error here if installing on an OS

older than XP, but disregard).

• In “Motherboard Driver Installer” window, click “Install”.

• In pop-up window, click on “Install the Driver Software Anyway”

(Win 7 and Win 8 only).

• Click “OK”, and then click “Finish”.

The following instructions apply only to non WIN 7 and WIN8

systems:

• After the software install, plug in the USB cable and

motherboard, and the hardware installation wizard should

appear.

• If asked for the location of drivers, use C:/Program Files

(x86)/Intersil/RTC_EVAL/USB_Driver directory as the source.

Note (x86) only for WIN7 & WIN8 Systems.

• Click “Next” to install the drivers and then “Finish” to complete

the installation.

The installation program places the RTC evaluation software

(RTC13.exe) in: C:\Program Files (x86)\Intersil\RTC Eval on a

WIN7 and WIN8 PC, or in C:\Program Files\Intersil\RTC Eval on

an XP or older PC.

Using the Software

To start the evaluation software, double click on the Desktop

“RTC Evaluation” icon, or double click on C:\Program

Files\Intersil\RTC Eval\RTC13.exe and the GUI (Graphical User

Interface) should appear as shown in Figure 1. This first screen is

the “Setup” page, as indicated on the function tab near the top of

the GUI. The screen’s bottom margin contains USB connection

status messages, with the center message indicating if the USB

device is disconnected or active.

There are multiple tabs (e.g., “Set Clock”) at the top of the GUI.

These tabs take the user to screens for setting up the RTC and for

controlling its functions, and each of the tabs is discussed in the

following sections.

There are icons in the top tool bar to print the register contents

and the “Graph” screen deviation plot, and to control VDD to the

daughterboard. The printer icon prints the current register values,

and the “RTC Deviation” plot from the “Graph” screen, to the PC’s

default printer. To print the actual register values, the user must

first use the “Register” tab to read the current contents of all

registers. Simply select a register group from the drop-down box,

and then click the “Page Operation” “Read” button. Repeat the

process until all register groups have been read, and it is best to

read the “RTC” group last, so the time/date registers are as up to

date as possible. The switch icon toggles the daughtercard VDD

from disabled (open switch icon) to enabled (closed switch icon),

and vice versa. The icons remain visible from all screens, as do

the polled RTC values displayed in the right-hand margin.

There are three common causes if the following error box

appears during a read or write cycle with the RTC:

1. The PC has powered down, gone into screen lock, and

powered back up. Unplugging and replugging the USB cable

fixes this problem.

2. The “VDD Enabled” check box on the “Setup” screen isn’t

checked, or

3. The daughtercard’s “DEV VCC” (or “JVDD”) jumper is missing.

Correcting these three problems should eliminate the error.

“SETUP” TAB

There are three sections to the Setup screen, plus a

time/date/temperature display section. The left section

indicates the selected RTC device, and that RTC’s features are

listed in the large text box. RTC selection is via the drop-down

box, and the device selection determines which other tabs the

GUI displays.

The middle left section has five functions. The “VDD Enabled”

check box controls the motherboard’s RTC VDD switch. Clicking

this check box enables or disables VDD to the daughterboard,

and to the I2C pull-up resistors. Note that when this box is

unchecked, no communication with the RTC daughterboard is

possible. The switch icon in the GUI’s top tool bar performs the

same function as the “VDD Enabled” check box. With VDD on,

clicking the switch icon shuts off the daughterboard’s VDD, and

the icon displays an open switch. Clicking the icon again,

reapplies VDD and the icon displays a closed switch. The I2C bus

speed - either 100kHz or 400kHz - is selected from the middle

drop-down box. The temperature sensor type (daughterboards

have either an LM75 or an LM76) is selected via the two “radio”

buttons, with the default value being the more common “LM75”.

A nonsensical reading in the “LM75 Temperature” box in the

right-hand margin may indicate that the daughterboard contains

an LM76. The sensor’s temperature value can be calibrated by

adding an offset to the sensor reading via the “Temperature

Calibration” box. Set the “Eval Board Select” drop-down box to

“USB RTC”.

The middle right section is the Status register display and event

reset section (this latter feature is only for the ISL1208 through

ISL1221). The relevant status bits for the selected RTC are

displayed as lights in the upper section and those bits can be

cleared using the buttons in the lower section.

Application Note 1745

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October 9, 2013

Time, Date, and Temperature readings are displayed in the right-

hand margin, regardless of which function tab is selected, and

this section contains the following information:

•PC Time - The time kept on the PC; displayed all the time.

•RTC Time - The time currently stored in the RTC’s time

registers, displayed only if polling is enabled (i.e., box is

checked at bottom of right-hand margin). The display matches

the RTC’s selected time format (i.e., 12 or 24 hour mode).

•RTC Deviation - The current delta between RTC time and PC

time.

•PC date - The current date kept on the PC; displayed all the

time.

•RTC date - The date currently stored in the RTC’s date, month,

and year registers, displayed only if polling is enabled.

•Temperature - The current reading of the daughterboard

temperature sensor, displayed if polling is enabled. If there is

no temperature sensor the window is blank. Most Intersil RTC

daughterboards use the LM75 device. Older daughterboards

may have used the LM76 device, so if the reading is way off,

try clicking the “radio” button labeled “LM76” in the

“Temperature Calibration” section.

•Enable Polling - Checking this box causes the software to

automatically poll the time/date, status, and LM75

temperature registers every second. The results are displayed

in this right-hand side GUI section, and the Status register

results are reflected in the state of the LEDs on the various

screens.

Polling Caveats - Polling can confound user initiated Status

1) Some devices (e.g., ISL12026/26A) reset the Status

enabled, a set alarm bit resets within a second, due to the next

polling cycle. Thus, a user initiated Status register read after a

polling cycle may return alarm bits as zeros, even though an

alarm occurred. To prevent this, click on the “Enable Polling”

check box - to uncheck it and thereby disable polling - while

evaluating the ISL12026 alarms.

2) Setting the ARST bit in the Status register in many devices

causes alarm bits and some other status bits (e.g., ISL12082

TMR and BAT bits) to reset after a Status register read. Again,

the solution is to disable polling while evaluating the ARST and

alarm functions.

“SET CLOCK” TAB

This tab contains two sections for setting the RTC’s time/date. The

“Time and Date Selection” section (left side) allows the user to

select the desired RTC time, date, and format. The time may be

typed into the “Set Time” boxes (do not enter the leading “0” in the

hours box if using 12 hour format), or clicking in an individual box

allows the GUI’s up and down arrow keys (to the right of the boxes) to

increment or decrement the current entry. Select the month, date,

and year from the calendar section below the “Set Time” boxes

(note: the day of the week is not set when you use this section).

The middle section actually writes the RTC with either the user

selected data, as described in the previous paragraph, or with the

PC’s current time. The buttons that trigger these actions are

described in the following.

One advantage of using this screen to set the RTC time is that the

software automatically handles the time/date register (i.e., “RTC”

registers) “interlock” that is incorporated in most Intersil RTC

devices. See the “Registers Tab” section below for details. After

FIGURE 1. EVALUATION SOFTWARE GUI MAIN TAB (SETUP)

Application Note 1745

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October 9, 2013

using the “Set Clock” function, and if polling is enabled, the new RTC

time/date are displayed in the right-hand margin.

The “buttons” on this screen perform the following functions:

•Write RTC Eval Board from PC Clock - Clicking this button reads

the PC’s time and date values, and writes them to the RTC’s

registers. This is a one button method to completely initialize the

RTC’s time/date registers.

•Set RTC Date and Time - Use this button to write the data from the

“Time and Date Selection” section into the RTC’s registers.

•Get RTC Date and Time - Clicking this button populates the “Time

and Date Selection” windows with the RTC’s current time/date.

These values can then be edited, and rewritten to the RTC.

•Set PC Time and Date from RTC Eval Board - This button writes

the RTC’s current time/date to the PC’s clock. Using this

button is not encouraged, as the current PC time and date are

lost.

“REGISTERS” TAB

This tab enables reading from, and writing to, any of the registers

in the selected RTC device. Pick a register - or register group -

from the drop-down box below the tabs, and the screen displays

those registers, but not their contents (cell’s gray shading

indicates an indeterminate value). Click on the “Page Operation”

“Read” button (below registers on the GUI’s left side), and the

registers’ contents are now displayed (white boxes represent

zeros, blue boxes represent ones). Initiating a page read is

always the recommended first step after selecting a register

group. The read populates the screen with current register

values, which helps prevent writing out of date data (e.g., a

previous time) into registers - or bits - that aren’t being actively

changed. The “Read” button at the right of each register row

(under the “Byte Operation” heading) reads that individual

There are two ways to set the data when writing to a register:

1) Enter the hex value for the desired data into the “Hex” column

to the right of the register’s name. Note that the register’s

displayed data changes to match the hex code.

2) Enter the desired value bit-by-bit in the register cells. To

change an individual bit, click on it to toggle its value. Note that

clicking a bit in an unread register - i.e., the cell colors are gray -

does not cause a register read, so the data subsequently

displayed are not the register’s true contents. Clicking the

data to be written to the register(s), so it is strongly

recommended that a register or page read be executed

immediately before changing any register bits.

After editing a register’s contents, click the “Byte Operation”

column “Write” button to write a single register, or click the “Page

Operation” “Write” button after updating multiple registers.

Operations initiated on screens under other function tabs may

change the RTC’s registers, and those results are only displayed

on the “Registers” screen after a subsequent read operation.

Also, changes made on the Registers screen are reflected on the

corresponding function’s screen only after clicking that

tab/function’s “Read” button. When reading the Status register,

note the “Polling Caveats” listed at the bottom of the previous

“Setup Tab” section.

Time/Date Register Interlocks

Nearly all Intersil RTC devices have an interlock feature that

requires special bits to be set before the time/date (“RTC”)

registers can be written. The majority of interlocked devices (e.g.,

the ISL1208) have a “WRTC” bit in the Status or INT register, and

this bit must be written to a “1” before the RTC registers can be

written. The evaluation software does NOT return an error if the

user attempts to write the RTC registers when WRTC=0, so you

must remember to check the state of the WRTC bit if the time

doesn’t update after the write cycle.

The ISL12024/25/26/27/28/29 use a two bit, Status register

WEL/RWEL interlock, where a special combination of writes is

required to unlock any register (RTC, Status, Control, Alarm, etc.)

for writing. To simplify register writes, this family’s Register

screens include an “Unlock” button, and an “Enable Auto Unlock”

check box. Checking the “Enable Auto Unlock” box (software’s

default setting) causes the software to automatically set the WEL

and RWEL bits during each write command, so the user doesn’t

have to worry about unlocking the registers. Clicking the “Unlock”

button causes the evaluation software to properly set the WEL

and RWEL bits, so a subsequent write command executes as

desired. Note that the RWEL bit resets after every register write

cycle (WEL stays set), so click the “Unlock” button before every

Unlock” function. A few devices (ISL12008, ISL12057,

ISL12058, ISL12059) have no interlock, so the time registers

can be written without being unlocked.

“SRAM” OR “EEPROM” TAB

This tab allows the user access to the on-chip general purpose

memory, if the RTC has it. The memory is battery backed SRAM

on some devices (ISL12020M/22/22AM/22M/32), and

EEPROM on others (ISL12024-29).

To read or write an individual memory byte, click on the cell in the

displayed matrix, and the address appears in the “Byte R/W”

section. Click the “Read” button to see the cell’s contents, or

enter the hex data in the box next to the “Write-Adr” box, and

click the “Write” button to change the byte. Click the “Read” or

“Read All” button to display what was just written.

To show all the memory bytes’ contents in the display matrix,

click the “Read All” button, noting that the memory may contain

random data if it has not been written previously. If desired, all of

the memory bytes may be written simultaneously using the

“Write All” button. First, select one of the “Fill Options” by clicking

one of the four “radio” buttons under that heading. “Data=Adr”

writes the cell’s address into its memory location, while

“Checkerboard” writes the two user defined data bytes to

adjacent memory bytes. “Explicit1” and “Explicit2” allow the user

to define two different data bytes that may be written to the

entire memory array. After choosing the desired fill option, click

the “Write All” button to write the memory array. Remember to

click “Read All” to display what was just written.

“GRAPH” TAB

The RTC evaluation software records continuous measurements

of the RTC time to PC reference clock deviation, and of the board

temperature. The Graph tab then allows the user to display the

results vs. elapsed time, for times extending from a few minutes

to thirty days.

Application Note 1745

5AN1745.2

October 9, 2013

To create a graph, select the “Deviation Range” from the drop-

down box in the lower left corner, and select the “Temp Range”

from the box on the right, to set the vertical axes’ ranges. Select

the “Time Base” (measurement time duration) from the box in

the middle, to define the horizontal axis range. Note that the

ranges may be changed at any time, and the data scales

accordingly. Data exceeding the “Time Base” is still collected,

and is displayed if the time base is increased.

Set the RTC time from the PC time as described previously. This

ensures that the RTC time matches the PC time when recording

starts. Ensure that the “Enable Polling” box is checked, and that

there is a near zero value in the “RTC Deviation” box in the right-

hand margin.

To begin recording, click the “Restart” button at the GUI’s bottom

right. The graph automatically records and plots the data as long

as the polling function is enabled. Graphing stops when polling is

disabled, and starts again when polling is re-enabled. Once re-

enabled, the new data point is plotted at the proper elapsed time

point. The graphing function connects the last data point to this

new data point, so the data between these two points is

meaningless. To start a new graph, click the “Restart” button.

Data is recorded periodically until polling is stopped. Multiple

samples are measured and averaged before being plotted on the

chart recorder.

The raw data can be saved to a file for analysis or for storage.

Choose a file directory and name using the “Open Folder” icon in

the tool bar, then click the “Save File” icon to save the chart data.

The top of the file contains a list of registers and values; see the

third paragraph of the “Using the Software” section for how to

ensure that the register list provides meaningful data.

Subsequent clicks on the save icon overwrite the previous file

with the latest data, without prompting for permission. The file is

overwritten even if it is open when save is clicked, but you will

have to close, and then reopen the file to see the updates.

The data collection start time remains in the “Start Time” box for

reference. Note that for long duration recordings of deviation, it is

advisable to use a PC program that automatically updates the PC

time, such as that available from NIST

http://www.boulder.nist.gov/timefreq/service/its.htm.

“INTERRUPT”, “FOUT”, AND “FOUT & IRQ” TABS

These tabs allow the user to select the frequency of the FOUT pin,

to select whether or not the FOUT pin is active in battery backup

mode, and on some devices (e.g., the ISL1208) to enable the

alarm IRQ output. Click the “Read” button to determine the

current state of the settings, and remember to click on the

“Write” button after making any changes to those settings (even

after clicking on a check box).

The drop-down box at the top left allows the selection of the FOUT

frequency. On many devices the first (0Hz) or last entry in the drop-

down box switches the multifunction IRQ/FOUT pin to the alarm

interrupt (IRQ) mode. The ISL12058 also requires the checking of

the “Enable Alarm1” box to activate the IRQ function, and the

ISL12057’s IRQ pin control is on the “Alarm & IRQ” screen.

Many of these RTC screens include a “Disable Frequency Out in

Battery Mode” check box, and checking this box disables the

FOUT pin whenever the RTC enters battery back-up mode.

“ALARM” TAB

The alarm tab provides an easy way for users to define software

alarms - indicated by the Status register alarm bits - and

hardware alarm interrupts (IRQ outputs), when available. Click

the “Read” button to determine the current state of the settings,

and remember to click on the “Write” button after making any

changes to those settings (even after clicking on a check box).

For the best results, set up the alarm time/date triggers before

enabling an alarm.

The screen provides drop-down boxes to select the alarm

time/date trigger conditions. Selecting “Ignore” in the drop-down

box prevents that time/date component from being used to

determine an alarm match. For example, a “10” in the “Seconds”

box with “Ignore” in all the other boxes means that an alarm is

generated whenever the time has “10” in the “seconds” position.

Note that the “Hours” drop-down box contains entries for both

military and 12 hour time formats, and the selected “Hours”

value must correspond to the chosen time format, or the alarm

will not trigger.

Check boxes at the top of most alarm set-up boxes control

whether or not an alarm is enabled (i.e., generates software

and/or hardware alarms), and select either normal or repetitive

pulsed interrupt mode (IM). Note that the actual hardware alarm

pin (IRQ output) usually is enabled via the “Interrupt” screen, as

previously described.

The “Alarm Status” “LED” below the alarm set-up box reflects the

Status register alarm bit state. The “Manual Clear Event”

button(s) at the GUI bottom resets the appropriate Status register

alarm bit, and thus the “LED”.

“EVENT” TAB (ISL1209, 1219, 1221, 12032 ONLY)

This tab appears if the chosen RTC includes an Event Detection -

also know as “Tamper Detection” - feature. This screen allows the

user to control the event detection parameters, and the event

time stamp functions, when available. Click the “Read” button to

determine the current state of the settings, and remember to

click on the “Write” button after making any changes to those

settings (even after clicking on a check box).

The left side of the screen contains the controls for the EV

function, and once checked and written it also activates the

sample rate (ESMPL) and hysteresis (EHYS) drop-down boxes.

The lower three check boxes select whether or not the RTC stops

incrementing the time once an event occurs (RTCHLT), whether

or not the event input (EVIN) pull-up current source is enabled

(EVIENB), and whether or not the event detection function is

enabled in battery backup mode (EVBATB). For these last two

functions, note that checking the box disables the function.

The right side of the screen includes the “Event Detect” “LED”,

and the event time stamp display window (not available on the

ISL1209). The LED indicates the Status register EVT bit state, but

is not available on the ISL12032. The ISL1219 and ISL1221 time

stamp register locks after the first event. Once the Status register

EVT bit is reset, the time stamp register unlocks, and records the

next event time stamp. The ISL12032 screen displays the first

event time stamp - which locks until cleared - the last three event

time stamps, and an event counter. The screen also includes

Application Note 1745

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buttons to read time stamps, and to clear the four time stamp

registers and the time stamp counter.

After setting up the parameters and enabling events, pushing the

“Event” button (S1 or EVIN) on the evaluation board lights the

“Event Detect” LED, and loads the current time into the time

stamp register (unless the register is locked).

“CRYSTAL COMP” TAB

This tab appears if the chosen RTC includes a crystal

compensation feature, which allows the user to calibrate out

crystal tolerances, or to compensate a crystal for temperature

effects. For most RTC devices, this screen includes control boxes

for the fine adjust analog trim (ATR) setting, and for the course

adjust digital trim (DTR) setting. Some devices also include a

Battery Mode ATR (BMATR) control box, which allows the user to

select a different level of compensation when the RTC is in

battery backup mode.

“SYSMGMT” TAB

This tab appears if the chosen RTC has an unusual system

feature. For example, this tab allows the software to control the

ISL12029’s programmable I2C bus watchdog timeout and

programmable low VDD Reset threshold functions. For the

ISL12032, this tab provides control over the RTC’s AC power

functions.

“DST” TAB

Select an RTC that includes a daylight savings time (DST)

function, and the evaluation software displays this tab. From this

screen the user can set the trigger time/date for the RTC to enter

DST (i.e., DST forward) and the trigger time/date for the RTC to

return to standard time (i.e., DST reverse). The “DST Forward

Adjust” “LED” reflects the state of the Status register DSTADJ bit,

so it lights when the RTC switches to DST, and it extinguishes

when the RTC returns to standard time. The LED does not light

when the RTC is initialized to a time between the “DST Forward”

and “DST Reverse” times.

Note: To get the daylight savings time adjustment (forward or

backward) to occur the next time the RTC time hits the trigger

setting, the set trigger time must be at least one hour after the

current RTC time when the DST function is enabled (by checking

this screen’s “DST Enable” check box, or by setting the DstMoFd

“TEMPCOMP” TAB

The ISL12022, ISL12020M, ISL12022M, and ISL12022MA

feature an on-chip temperature sensor, and accompanying

crystal temperature compensation circuitry, and this tab controls

those functions. Click the “Read” buttons to determine the

current state of the settings, and remember to click on the

appropriate “Write” button after making any changes to those

settings (even after clicking on a check box). The “Write Mode”

and “Read Mode” buttons operate on the entries in the

“Temperature Sense Control” box, while the “Write Comp Regs”

and “Read Comp Regs” buttons operate on the entries in the

“Temp Coefficient & Gain”, “Final Trim”, and “Initial Trim” boxes.

The ISL12022 operation is different than the ISL12020M and

ISL12022M, in that the ISL12022 “Temp Coefficient & Gain”

registers are writable, while they are “Read Only” on the other

two RTCs. Before writing these ISL12022 registers, make sure

that temperature sensing is disabled (i.e., uncheck the “Temp

Sense Enable” [TSE] box, and click “Write Mode”).

Temperature sensing can be enabled for only normal VDD

operation (check only the TSE box), or for VDD and battery

backup operation. For all three RTCs, to enable temperature

sensing in both modes: click TSE first, then “Write Mode”, then

click “Battery Mode Temp Sense Enable” (BTSE) followed by

“Write Mode”. After writing BTSE note that the “TSE period in

Battery Mode” box changes from “OFF” to a time interval, which

is the interval at which temperature sensing occurs in battery

backup mode. Clicking the “Battery Mode Temp Sense Period”

box followed by “Write Mode” toggles the “TSE Period” box

between “10 Minute” (box unchecked), and “1 Minute” (box

checked).

After enabling temperature sensing, read the RTC’s temperature

by clicking the “Read Mode/Temp” button toward the bottom left

of the screen. Note that successive reads return the same

temperature value, unless a new sense cycle occurred.

The ISL12022X default, non-backup mode, temperature sense

interval is once per minute. Clicking the “Write Mode” button,

with the “TSE” box checked, forces an immediate sense cycle. To

force more frequent, automatic updates, go to the “Interrupt”

tab, and select an update interval from the “TSE Refresh” drop-

down box, and click “Write”. For example, selecting “5” from the

drop-down box causes the evaluation software to trigger a

temperature sense cycle every 5 seconds. The user must still

click “Read Mode/Temp” under the “TempComp” tab to display

the updated temperature.

“PWRMGMT” TAB

This tab appears if the chosen RTC includes low VDD and low

VBAT monitoring functions. From this screen the user can set the

desired trigger thresholds for the LVDD status bit, and for the

VBAT’s 85% (LBAT85) and 75% (LBAT75) threshold status bits.

This screen also displays time stamps that indicate when the RTC

first entered battery backup (VDD-to-VBAT), and when the RTC last

returned to VDD operation from battery backup (VBAT-to-VDD).

Time stamps may be cleared via the CLRTS button. The

ISL12032 includes an on-chip battery trickle charger, and the

control for this function is on the PWRMGMT screen.

Detailed Hardware Description

RTC USB Evaluation Platform - General

Description

The RTC evaluation hardware consists of a universal

motherboard, and a daughterboard specific to the RTC being

evaluated.

Application Note 1745

7AN1745.2

October 9, 2013

The motherboard contains all the main support functions for the

RTC device, including:

• A Microcontroller with a USB interface for communicating with

a PC and an I2C interface to communicate with the RTC.

•An I

2C Buffer IC for allowing variable I2C pull-up voltages.

• A 5V supply (VBUS from the USB) and a regulated 3.3V supply,

with a jumper to select either voltage to power the RTC device.

• Connectors for the USB interface and for the daughterboard.

• Provisions for RTC backup supply sources, including: a 100µF

supercapacitor, a 3.3V rechargeable Lithium battery position,

and a socket for a CR1220 3V Lithium coincell battery, with a

jumper to select the desired backup source.

• A MOSFET switch (M1), controlled by the evaluation software,

that disconnects the VDD supply from the daughterboard to

allow the RTC to operate from a backup power source.

• Test points for monitoring the SCL and SDA lines plus ground.

The daughterboard contains the RTC IC, a temperature sensor,

and all the components necessary for their operation. See the

“DAUGHTERBOARDS - Functional Description” on page 8 for

details.

Motherboard Functional Description (see

Figure 2 and Schematic in Appendix A on page 13)

MICROCONTROLLER

The microcontroller used is the Silicon Labs C8051F320. It

includes on-chip EEPROM, and a dedicated I2C serial interface

for communication with the Intersil RTC and the temperature

sensor on the daughterboard. The microcontroller’s power comes

directly from the USB interface’s VBUS (5V) connection. The

microcontroller generates the 3.3V supply used on the

motherboard and daughterboard. Note that the microcontroller’s

P1.0 to P1.4 I/O pins are available at the daughterboard

connector, J2, but no connections should be made to these pins.

J1 IS A MICROCONTROLLER PROGRAMMING

CONNECTOR AND SHOULD NOT BE USED.

POWER SUPPLY AND RTC VDD SUPPLY

The motherboard draws its power from the USB +5V ±5% supply.

If the evaluation board is used to provide power for other

circuitry, care must be taken to keep the +5V current draw well

below 500mA, which is the maximum for a USB hub-type device.

The motherboard produces a 3.3V supply capable of delivering

up to 10mA.

The VDD for the Intersil RTC chip, as well as for the serial

interface pull-up resistors, is selectable for either 3.3V or 5V

using J3. To use an external VDD supply, remove jumper J3, and

connect the supply to the J3 center pin. Using this configuration

allows the software controlled VDD switch to control power to the

RTC and to the I2C pull-ups. Several ground test points are also

available on the motherboard.

BACKUP SUPPLY (VBAT)

There are two sources of RTC backup supply available. A 100µF

supercapacitor (C8) is populated on the board, and it provides

enough backup power for the typical RTC chip to remain active for

several minutes at room temperature with VDD = 5V. There is also

a CR1220 battery socket (without the battery) to allow for easy

backup battery insertion/removal. This battery will last up to five

FIGURE 2. RTC EVB MOTHERBOARD LAYOUT

SUPERCAP

BACKUP

BATTERY

SOCKET

VDD SELECT

DAUGHTERBOARD

CONNECTOR

JUMPERS

FOR VBAT

SELECT

USB CONNECTOR

POSITION FOR A

RECHARGEABLE

BATTERY

(CR1220)

Application Note 1745

8AN1745.2

October 9, 2013

years in normal backup operation. The backup source is selectable

via jumper J4 as shown in Figure 2. The right-hand column of J4

connects to the RTC VBAT pin (J2 pin 9), and the other column

connects to the power sources. There are four positions possible

on J4: Supercap (SCAP), rechargeable battery (BT2, user must

install a suitable battery holder, but the charging diode [D2] and

resistor [R9] are populated), CR1220 Battery (BT1), and ground

(GND). If no backup is required, then the “GND” position should be

used. To use an alternate VBAT source, remove the jumper and

connect the source to any of the right-hand column pins.

DAUGHTERBOARD CONNECTOR (J2)

J2 is a 10 pin, female connector. The RTC daughterboard plugs

into this connector, which provides power - VDD, VBAT, and GND -

and interface signals (SDA, SCL) to the RTC device, and to other

components on the daughterboard. The signals are labeled on

the motherboard silkscreen.

USB CONNECTOR (CON1)

This connector is a standard USB type B connector, which

connects to the USB port of a PC using a USB type A-B cable

(included with the evaluation system). The cable must be

plugged into a PC for VDD power to be applied to the RTC, but

depending on the position of J4, the RTC may operate off backup

power with the cable disconnected.

POWER/USB ACTIVITY INDICATOR

There is one surface mounted LED - labeled “POWER” - on the

motherboard, which lights when the +5V power is available from

the USB cable. The LED blinks when the PC communicates with

the motherboard. For example, if polling is enabled the LED

blinks at about 1Hz.

SOFTWARE CONTROLLED RTC VDD SWITCH

Device M1 operates as a switch to control whether or not VDD is

applied to the RTC and to the I2C pull-up resistors. Note that

when VDD is turned off, the RTC device operates from the backup

power source, if one is selected by J4 on the motherboard. The

daughterboard’s VDD also powers the I2C SDA and SCL pull-up

resistors, so no communication with the RTC is possible when

VDD is switched off. If an RTC allows I2C communication in

battery backup, and if this function is desired, remove power to

the RTC via the daughterboard’s “Dev VCC” jumper (e.g., JP3 for

the ISL12032) rather than via this VDD switch.

DAUGHTERBOARDS - Functional Description

The daughterboards include the desired Intersil RTC device, and

have a 10-pin female connector (J1) that mates with the

motherboard connector. There are multiple jumpers on each

daughterboard, but the “DEV VCC” jumper (“JVDD” on newer

boards) is the only one required. The “DEV VCC” jumper supplies

VDD only to the RTC IC, so connecting an ammeter in place of the

jumper allows for measuring the RTC’s supply current. Other

headers connect power to pull-up resistors on RTC output pins, so

they may be removed if desired. The SDA and SCL pull-ups reside

on the motherboard, so none of the daughterboard jumpers

affect I2C communication.

Most daughterboards include a surface mount 32.768kHz,

CL = 12.5pF, ±10ppm tolerance crystal. Newer daughterboards

use a Citizen CM200C-32.768KEZF part number, but any

equivalent crystal works. Users may replace the stock crystal

with a ±20ppm version to reduce cost, or with a ±5ppm version if

better accuracy is desired. Note that the ISL12057 requires a

CL = 6pF crystal, and the included crystal is a ±20ppm version.

Most RTC outputs are open collector, so daughterboards include

pull-up resistors on these pins, with a jumper (FOUT or IRQ/Fout)

provided to remove power from the pull-up resistor, if desired.

Series LEDs are also included to indicate the output state

(ON = Low Output). Most daughterboards include an additional

jumper that allows the pull-up source to be switched from VDD to

VBAT, so an FOUT or IRQ that is active in backup mode can be

evaluated.

Devices that include event detection (ISL1209/19/21/32) have

an EVIN input connected to a “normally closed” pushbutton

switch on the daughterboard. Pushing this switch creates a

low-to-high transition on the EVIN input, which simulates the

occurrence of an “event”. A large value pull-up resistor also

connects to EVIN, and there is a jumper to power the pull-up from

VDD or from VBAT. When using the RTC’s EVIN internal pull-up

current source, remove this jumper.

The daughterboard includes a temperature sensor, which is used

to monitor temperature for crystal frequency drift testing, and for

the software’s “graph” function. When polling is enabled, the

evaluation software polls the temperature sensor along with the

RTC time and status.

The daughterboard schematics and layouts are included as

Figures 5 thru 8.

THE ISL12032 DAUGHTERBOARD

The ISL12032 device possesses many more features than the

other Intersil RTC devices, thus the evaluation daughterboard is a

bit more complex. The schematic is shown in Figure 3 and the

layout is in Figure 4.

AC INPUT

The ISL12032 can use an external 50Hz or 60Hz AC power clock

for the internal time clock. There are two ways to hook this up.

One way is to use a transformer with a sine wave output,

connected to JP1 (TFR). This input is conditioned by a selectable

voltage divider and AC coupled to an emitter follower, which

assures the peak voltages are never more than the VDD/GND of

the RTC device. The ratios for the resistor divider are as follows:

R11: 0.011 x VTRF

R12: 0.118 x VTRF

R13: 0.211 x VTRF

The TFR input has no polarity, connections can be reversed as

long as the transformer output used is not grounded. If the TFR

input is used, then a jumper MUST be placed across JP2, ACIN, so

that the clock signal reaches the RTC device.

If a single-ended sine wave or square wave clock source is used

(i.e., a waveform generator), it should be connected to the ACIN

jack at JP2-2, and the signal ground should connect to a nearby

ground. The amplitude should be from 1.5VP-P to 4VP-P.

Application Note 1745

9AN1745.2

October 9, 2013

EVENT FUNCTION

S1 is the Event Switch for the ISL12032, and jumper JP7 must be

installed to connect the switch leads to ground. Jumper JP8 can

be used to select an external pull-up resistor, with either device

VDD or Battery pull-up voltage. Remove JP8 if the internal pull-up

is used.

INDICATOR LEDS

JP4 and JP5 connect LEDs for the Event and IRQ- functions,

respectively. Remove these jumpers if no indicator is desired for

these functions.

D3 and D4 are indicator LEDs for the AC Ready and Low Voltage

detect functions, respectively. Thus, they do not have jumpers

and are active at all times.

OTHER FUNCTIONS

The FOUT function is at JP8-2. There is a ground connection at

JP8-1 for connecting an instrument (such as a frequency counter)

with a ground lead.

JP3 is the “DEV VCC” jumper. If device ICC current measurement

is desired, remove this jumper to insert an ammeter in the

circuit.

FIGURE 3. ISL12032 TSSOP EVALUATION DAUGHTERBOARD SCHEMATIC

Title

Size: Revi

SDA

SCL

1.2K

VCC_IN

VBAT

JP4

0.1uF

IRQ-

Jumper

DEVICE

VCC

1.2K

JP5

EVDETOUT

EVDET

Detect

Jumper

EVIN Detect

Switch

SDA

A0 7

GND

4TCA

3SCL

A1 6

INT 5

+VS 8

LM75

LTST-C230KRKT

LTST-C230KGKT

32.76 kHz

ISL12032 TSSOP EVAL DAUGHT

JP7

R4 5M 1

JP8

VBAT

GND

EVIN

7EVDET 8

FOUT 9

ACRDY 10

SDA 11

SCL 12

IRQ 13

VCC 14

ISL12032

JP6

EVIN

VBAT

VCC_DEV

JP1

10k

MMBT3904

VCC_IN

JP2

IRQ

EVDETOUT

FOUT

Jumper

0.01uF

FOUT

LTST-C230KRKT

1.2K

VCC_IN

ACRDY

GND1GND2

TP4 ACR

TP5

SDA

SCL

GND3

JP3

10 uF

R16

43K

R10

68K

R11

820

R12

10K

R13

20K

R14

75K

R15

1 uF

JP9

1uF

TFR

EVIN

Pullup

Application Note 1745

Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is

cautioned to verify that the Application Note or Technical Brief is current before proceeding.

For information regarding Intersil Corporation and its products, see www.intersil.com

AN1745.2

October 9, 2013

FIGURE 4. ISL12032 DAUGHTERBOARD LAYOUT

Application Note 1745

11 AN1745.2

October 9, 2013

FIGURE 5. ISL12020M/22M EVAL DAUGHTERBOARD SCHEMATIC

JPUSPLY

JVDD

GND

SDA

SCL

JBAT

VBAT

VDD

JLVRST

1kΩ

IRQ_FOUT

LVRST

C3 C5

LM75

SDA

SDL

ISL12020M

ISL12022M

SDA

SCL

0Ω

ISL12020M = DNP = R2, R3

ISL12022M = DNP = R2, R5

20 LD SOIC

20 LD DFN

0.1µF

GND

SDA

SCL

VDD

GND

VDD

IRQFOUT

IRQ/FOUT

VBAT

GND

VDD

GND

SDA

SDL A0

FIGURE 6. ISL12020M/22M EVAL DAUGHTERBOARD LAYOUT

Application Note 1745

12 AN1745.2

October 9, 2013

FIGURE 7. ISL1208/09/18/19/20/21/008/022/024/025/026/027/057/058/059/082 8LD SOIC AND 10LD MSOP EVALUATION

DAUGHTERBOARD SCHEMATIC

JPUSPLY

JVDD

GND

SDA

SCL

JBAT

VBAT

VDD

1kΩ

C3 C5

SDA

SDL

SDA

SCL

ISL1208/18/008/022 = DNP = U3, R2, R4-R6, R8, R9, C2, C4, C5

8 LD SOIC

10 LD MSOP

LM75

JEVSPLY

1R9

1MΩ

JEVIN

EVIN

DNP

SDA

SCL

PIN7_9

PIN3

PIN6

0Ω

0.1µF 0.1µF

0.1µF

0Ω

0.1µF

ISL1209/19/21 = DNP = U2, R2-R4, R6, R8, C3, C4

ISL12057 = DNP = U3, R2-R4, R8, R9, C2, C4, C5

ISL12058/59 = DNP = U3, R2-R6, R8, R9, C2, C4, C5

ISL12024/25/26/27 = DNP = U3, R2, R3, R5-R7, R9, C2, C5

ISL1220/082 = DNP = U2, R2-R4, R6, R8, R9, C3, C4

GND SDA

SCL

VDD

# REFER TO PARTS DATA SHEET PINOUT FOR PIN NAME

GND

VBA

SDA

SCL

VDD

GND

SDA

SDL A0

FIGURE 8. ISL1208/09/18/19/20/21/008/022/024/025/026/027/057/058/059/082 8LD SOIC AND 10LD MSOP EVALUATION

DAUGHTERBOARD SCHEMATIC

Application Note 1745

13 AN1745.2

October 9, 2013

Appendix A: RTC Motherboard Schematic

Mouser Electronics

Authorized Distributor

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