
TMS29LF040, TMS29VF040
524288 BY 8-BIT
FLASH MEMORIES
SMJS825D – SEPTEMBER 1995 – REVISED JUNE 1998
6
POST OFFICE BOX 1443
HOUSTON, TEXAS 77251–1443
algorithm selection mode
The algorithm-selection mode provides access to a binary code that matches the device with its proper
programming- and erase-command operations. This mode is activated when VID (11.5 V to 12.5 V) is placed
on address pin A9. Address pins A1 and A6 must be logic low. Two bytes of code are accessed by toggling the
address pin A0 from VIL to VIH. All other address pins can be logic low or logic high.
The algorithm-selection code also can be read by using the command register, which is useful when VID is not
available to be placed on address pin A9. Table 2 lists the binary algorithm-selection codes for the
TMS29xF040.
Table 2. Algorithm-Selection Codes
ALGORITHM SELECTION
A0
DQ7
DQ6
DQ5
DQ4
DQ3
DQ2
DQ1
DQ0
HEX
Byte 0
0
1
0
1
0
1
97h
Byte 1
1
0
1
0
1
0
94h
A1 = VIL, A6 = VIL, E = VIL, G = VIL
erasure and programming
Erasure and programming of the TMS29xF040 are accomplished by writing a sequence of commands using
standard microprocessor write timings. The commands are written to a command register and input to the
command-state machine (CSM). The CSM interprets the command entered and initiates program, erase,
suspend, and resume operations as instructed. The CSM acts as the interface between the write-state machine
(WSM) and the external chip operations. The WSM controls all voltage
generation, pulse generation,
preconditioning, and verification of the memory contents. Program and sector/chip-erase functions are fully
automatic. When the end of a program or erase operation is reached, the device internally resets to the read
mode. If a byte-program or chip-erase operation is in progress, additional program/erase commands are
ignored until the operation in progress is completed.
command definitions
Device operating modes are selected by writing specific address and data sequences into the command
register. Table 3 defines the valid command sequences. Writing incorrect address and data values or writing
them in the incorrect sequence causes the device to reset to the read mode. The command register does not
occupy an addressable memory location. The register stores the command sequence along with the address
and data needed by the memory array. Commands are written by setting E = VIL and G = VIH and bringing W
from VIH to VIL. Addresses are latched on the falling edge of W and data is latched on the rising edge of W.
Holding W = VIL and toggling E is an alternative method. See the byte-program and chip/sector-erase sections
for a more complete description.