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The UM232H is a USB-to-serial/FIFO development module in the FTDI product range which utilizes the

FT232H USB Hi-Speed (480Mb/s) single-port bridge chip to handle the USB signaling and protocols. The

UM232H is ideal for development purposes to quickly prove functionality of adding USB to a target design.

The UM232H is a module designed to plug into a standard 0.6” wide 28 pin DIP socket. The USB connection

to a host system is via a mini-B USB connector. All components used, including the FT232H, are Pb-free

(RoHS compliant).

along with the four interface lines. In addition to these, the FT232H supports a CPU-Style FIFO mode and a

fast serial interface mode. It also introduces a half-duplex FT1248 interface that provides a flexible data

communication and high performance interface between the FT232H device and external logic. For further

details on the FT232H and the FT1248 mode, please refer to the FT232H datasheet and application note

Table of Contents

Appendix B – List of Tables & Figures ................................ 26

List of Tables ................................................................................... 26

List of Figures ................................................................................. 26

Appendix C – Revision History ........................................... 27

The UM232H module is used for prototyping and evaluation in an application using the FT232H.

The UM232H development module requires USB device drivers, available free from FTDI website. There is

the Virtual Com Port driver which allows the UM232H to appear as a serial port allowing legacy applications

for serial ports to function over USB (for example TTY). Another FTDI USB driver, the D2XX driver, can also

be used with application software to directly access the FT232H on the UM232H through a DLL.

version 4.2 onwards.

The UM232H has the following features:

controls the UART data, 245 FIFO data, Fast Serial (opto isolation) or Bit-Bang mode that can be selected

by SETUP (SetBitMode) command. Each Multi-Purpose UART/FIFO Controller also contains an MPSSE

(Multi-Protocol Synchronous Serial Engine). Using this MPSSE, the Multi-Purpose Serial/FIFO Controller can

USB Protocol Engine and FIFO control. The USB Protocol Engine controls and manages the interface

between the UTMI PHY and the FIFOs of the chip. It also handles power management and the USB protocol

specification.

Port FIFO TX Buffer (1Kbytes). Data from the Host PC is stored in these buffers to be used by the Multi-

RESET Generator – The integrated Reset Generator Cell provides a reliable power-on reset to the device

internal circuitry at power up. The RESET# input pin allows an external device to reset the FT232H. RESET#

should be tied to VCCIO (+3.3V) if not being used.

Baud Rate Generators – The Baud Rate Generators provides an x16 or an x10 clock input to the UART’s

from a 120MHz reference clock and consists of 14-bit pre-scaler and 4 register bits, which provide fine-

tuning of the baud rate (used to divide by a number plus a fraction). This determines the Baud Rate of the

UART, which is programmable from 183 baud to 12 Mbaud. See FTDI application note AN_120 for more

details.

+1.8/3.3V LDO Regulator. The +3.3/+1.8V LDO regulator generates +1.8 volts for the core and the USB

transceiver cell and +3.3V for the IO and the internal PLL and USB PHY power supply.

UTMI PHY. The Universal Transceiver Macrocell Interface (UTMI) physical interface cell. This block handles

the Full speed / Hi-Speed SERDES (serialise – deserialise) function for the USB TX/RX data. It also provides

the clocks for the rest of the chip. A 12 MHz crystal must be connected to the OSCI and OSCO pins or 12

MHz Oscillator must be connected to the OSCI, and the OSCO is left unconnected. A 12K Ohm resistor

should be connected between REF and GND on the PCB.

The UTMI PHY functions include:

The signal labels and pin designators for each pin of the UM232H is illustrated in Figure 2.

The UM232H Module can be configured as USB Bus-Powered or USB Self-Powered. This section describes

how to configure the UM232H for a number of different power supply arrangements.

Bus powered configuration, where the +5V supply that powers the module is sourced from the USB bus,

chip voltage regulator input of the FT232H via pin 5V0 (J1-2).

Connecting J2-2 (VIO) (power input for core of the FT232H) and J2-3 (3V3) (power output from the

FT232H) powers the VCCIO, VPLL and VPHY pins of the FT232H chip.

A USB Bus Powered device gets its power from the USB bus. Basic rules for USB Bus power devices are as

follows –

I. On plug-in to USB, the device must draw no more than 100mA.

II. On USB Suspend the device must draw no more than 500μA.

external logic would take its power supply from the USB bus (either the 5V on the USB pin, or 3.3V on the

3V3 pin).

Figure 5 – Bus Powered with Power Switching Configuration

USB Bus Powered circuits need to be able to power down in USB suspend mode in order to meet the

<=500μA total USB suspend current requirement (including external logic). Some external hardware can

power itself down into a low current state by monitoring the PWREN# signal. For external logic that cannot

power itself down in this way the FT232H provides a simple but effective way of turning off power to

external circuitry during USB suspend.

The values used here allow attached circuitry to power up with a slew rate of ~12.5V per millisecond, in

A 100kΩ resistor to VBUS creates a week pull up on the gate, this can prevent current from flowing through

the transistor during a power up or power down of the FT232H. Alternatively, a dedicated power switch I.C.

with inbuilt “soft-start” can be used instead of a MOSFET. A suitable power switch I.C. for such an

application would be a Micrel (www.micrel.com) MIC2025-2BM or equivalent.

Please note the following points in connection with power controlled designs:

i) The logic to be controlled must have its own reset circuitry so that it will automatically reset itself

when power is applied on coming out of suspend.

internal EEPROM to inform the system of its power requirements.

circuitry (the PWREN# signal gets its VCC supply from VIO). Either connect the power switch between

the output of the 3.3V regulator and the external 3.3V logic or power VIO from the 3V3 pin of the

FT232H.

supply

Figure 6 – Self-Powered Configuration – 5V0 External Supply

i) A Self Powered device should not force current down the USB bus when the USB Host or Hub

Controller use powered down.

ii) A Self Powered Device can use as much current as it likes during normal operation and USB suspend

as it has its own power supply.

iii) A Self Powered Device can be used with any USB Host and both Bus and Self Powered USB Hub. In

this case, the power descriptor in the internal EEPROM should be programmed to a value of zero

(Self-Powered).

In order to meet requirement (i) the USB Power is used to control the RESET# Pin of the FT232H device.

When the USB Host or Hub is powered up the internal 1.5kΩ resistor on USBDP is pulled up to 3.3V, thus

cause some USB host or hub controllers to power up erratically.

Note: When the FT232H is in reset, the UART interface pins all go tristate. These pins have internal 200kΩ

pull-up resistors to VCCIO, so they will gently pull high unless driven by some external logic.

example uses TXD and RXD for transmission and reception of data and RTS# / CTS# hardware

handshaking.

as connecting the reset to the a pull-up network. However, the PWRSAV# function has the additional

feature of being able to put FT232H into sleep mode when the USB host is powered down. There is one

trade of o using reset instead of PWRSAV#, in MPSSE mode the ACBUS7 pin can be selected as a GPIO pin,

using this pin from both PWRSAV# and GPIO mode can cause a conflict. PWRSAV# is enabled and disabled

using the EEPROM, this function is disabled by default. Figure 7 illustrates an alternative USB Self-Power

configuration.

Figure 7 – Alternative Self-Powered Configuration – 5V0 External Supply

Figure 8 illustrates the UM232H in a typical USB Self-Powered configuration similar to Figure 7. The

the 5V0 (+3V3 power supply input can also be supplied to 5V0 pin), VIO and 3V3 pins of the modules.

Please note that when the UM232H running from +3V3, the 3V3 pin becomes an input. The VIO and 3V3

pins connection provides 3V3 to the VCCIOs, VPLL and VPHY on the FT232H chip.

Figure 9 – Alternative Self-Powered Configuration – 3V3 External Supply

The FT232H uses an external EEPROM (on the UM232H module). This EEPROM can be programmed over

USB using FT_Prog. The default settings of the EEPROM are shown in the following table:

System and equipment manufacturers and designers are responsible to ensure that their systems, and any Future Technology Devices

Appendix A – References