M29W320DT, M29W320DB
10/44
SIGNA L DESCRIPTIONS
See Figure 2, Logic Diag ram, and T able 1, Sign al
Names, for a brief overview of the s ignals connect -
ed to this device.
Address Inputs (A0-A20). The Address Inputs
select the cell s in the memory arra y to access dur-
ing Bus Read operations. During Bus Writ e opera-
tions they control the commands sent to the
Comman d Interface of the internal state ma chine.
Data Inputs/Outputs (DQ0-DQ7). The Data I/O
outputs the data stored at the selected address
during a Bus Read operation. During Bus Write
operations they represent the commands sent to
the Command Interface of the internal state ma-
chine.
Data Inputs/Output s (DQ8-DQ14). The Data I/O
outputs the data stored at the selected address
during a Bus Re ad operation when B Y TE is High,
VIH. When BYTE is Low, VIL, these pins are not
used and are high impedance. During Bus Write
operations the Command Register does not use
these bits. When reading the Status Register
these bits should be ignored.
Data Input/Output or Address Input (DQ15A–1).
When BYTE is High, VIH, this pin behaves as a
Data Input/Output pin (as DQ8-DQ14). When
BYTE is Low, VIL, this pin behav es as an address
pin; DQ15A–1 Low wil l select t he LSB of the Word
on the other addresses, DQ15A–1 High will select
the MSB. Throughout the t ext consider references
to the Data Input/Output to include this pin when
BYTE is High and references to the Address In-
puts to inclu de this pin when B YTE is Low e xcept
when stated explicitly otherwise.
Chip Enable (E). The Chip Enable, E, activates
the memor y, allowing Bus Read and Bus Wr ite op-
erations to be performed. When Chip Enable is
High, VIH, all other pins are ignored.
Output Enable (G). The Output Enable, G, con-
trols th e Bus Read operation of the memory.
Write Enable (W). The Write Enable, W, controls
the Bus Write operation of the memory’s Com-
ma nd Inte r face .
VPP/Write Protect (VPP/WP). The VPP/Write
Protect
pin provides two functions. The VPP f unc-
tion allows the memory to use an external high
volt age po wer su pply to r educ e the time req ui re d
for Unlock Bypass Program operations. The
Wri t e Pro tec t fu nct io n prov i des a ha rd ware me th-
od of protecting the 16 Kbyte Boot Block. The
VPP/Write Protect pin must not be left floating or
unconnected.
When VPP/Write Prote ct i s L ow , VIL, the me mo r y
protects the 16 Kbyte Boot Block; Program and
Erase operations in this block are ignored while
VPP/Write Protect is Low.
W hen VPP/Write P rotect is High, VIH, the memor y
reverts to the previou s protection status of the 16
Kbyte boot block. Program and Erase operations
can now modify the data in the 16 Kbyte Boot
Block unless the block is protected using Block
Protection.
When VPP/Write Protect is raised t o VPP the mem-
ory automat ically enters the Unlock Bypass mode.
When V PP/Write Protect returns to VIH or VIL nor-
mal operation resumes. During Unlock Bypass
Program operations the memory draws IPP from
the pin to supply the progr amming circuits. See the
description of th e Unlock B y pass c ommand in the
Command Interface section. The transitions from
VIH to VPP and from VPP to VIH must be slower
than tVHVPP, see Figure 15.
Never raise VPP/Write Protect to VPP from any
mode except Read mode, otherwise the memory
may be left in an indeterm inat e state.
A 0.1µF capacitor should be connected between
the VPP/Write Protect pin and the VSS Ground pin
to decouple the current surges from the power
supply. The PCB track widths must be sufficient to
carry the curren ts required during Unlock Bypass
Program, IPP.
Reset/Block Temporar y Unprotect (RP). The
Reset/Block Temporary Unprotect pin can be
used to apply a Hardwar e Reset to the memory or
to temporarily u nprotect al l Block s that have been
protected.
Note that if VPP/WP is at VIL, then the 16 KByte
outermost boot block will remain protect even if RP
is at VID.
A Hardware Reset is achieved by holding Reset/
Block Temporary Unprotect Low, VIL, for at least
tPLPX. After Reset/Block Temporary Unprotect
goes High, V IH, the memory will be ready for Bus
Read and Bus Write operations after tPHEL or
tRHEL, whichever occurs last. See the Ready/ Busy
Output section, Table 15 and Figure 14, Reset/
Temporary Unprot ect AC Characte ristics for more
details.
Holding RP at VID will temporarily unprotect the
protected Blocks in the memory. Program and
Erase operations on all blocks will be possible.
The transition from VIH to VID must be slower than
tPHPHH.
Ready/Busy Output (RB). The Ready/Busy pin
is an open-drain output that can be used to identify
when the device is performing a Program or Erase
operation. During Program or Erase operations
Ready/Busy is Low, V OL. Ready/Busy is high-im-
pedance during Read mode, Auto Select mode
and Erase Suspend m ode.