A D V A N C E I N F O R M A T I O N
DEVICE BUS OPERATIONS
This section describes the requirements and use of the
device bus operations, which are initiated through the
internal command register. The command register
itself does not occupy any addressable memory loca-
tion. The register is composed of latches that store the
commands, along with the address and data informa-
tion needed to execute the command. The contents of
the register serve as inputs to the internal state
machine. The state machine outputs dictate the func-
tion of the device. Table 1 lists the device bus opera-
tions, the inputs and control levels they require, and the
resulting output. The following subsections describe
each of these operations in further detail.
Table 1. Am29SL400D Device Bus Operations
DQ8–DQ15
BYTE#
Addresses
(Note 1)
DQ0– BYTE#
Operation
CE# OE# WE# RESET#
DQ7
= V
= V
IH
IL
Read
Write
L
L
L
H
L
H
H
A
A
D
D
OUT
IN
IN
OUT
DQ8–DQ14 = High-Z,
DQ15 = A-1
H
D
D
IN
IN
V
0.2 V
±
V
0.2 V
±
CC
CC
Standby
X
X
X
High-Z High-Z
High-Z
Output Disable
Reset
L
H
X
H
X
H
L
X
X
High-Z High-Z
High-Z High-Z
High-Z
High-Z
X
Sector Address,
A6 = L, A1 = H,
A0 = L
Sector Protect (Note 2)
L
H
L
V
D
X
X
X
ID
IN
Sector Address,
A6 = H, A1 = H,
A0 = L
Sector Unprotect (Note 2)
L
H
X
L
V
V
D
D
X
ID
ID
IN
IN
Temporary Sector Unprotect
X
X
A
D
High-Z
IN
IN
Legend:
L = Logic Low = V , H = Logic High = V , V = 10 ± ±1.0 V, X = Don’t Care, A = Address In, D = Data In, D = Data Out
IL
IH
ID
IN
IN
OUT
Notes:
1. Addresses are A17:A0 in word mode (BYTE# = V ), A17:A-1 in byte mode (BYTE# = V ).
IH
IL
2. The sector protect and sector unprotect functions may also be implemented via programming equipment. See the “Sector
Protection/Unprotection” section.
control and selects the device. OE# is the output
control and gates array data to the output pins. WE#
Word/Byte Configuration
The BYTE# pin controls whether the device data I/O
pins DQ15–DQ0 operate in the byte or word configura-
tion. If the BYTE# pin is set at logic ‘1’, the device is in
word configuration, DQ15–DQ0 are active and con-
trolled by CE# and OE#.
should remain at V . The BYTE# pin determines
IH
whether the device outputs array data in words or
bytes.
The internal state machine is set for reading array data
upon device power-up, or after a hardware reset. This
ensures that no spurious alteration of the memory
content occurs during the power transition. No
command is necessary in this mode to obtain array
data. Standard microprocessor read cycles that assert
valid addresses on the device address inputs produce
valid data on the device data outputs. The device
remains enabled for read access until the command
register contents are altered.
If the BYTE# pin is set at logic ‘0’, the device is in byte
configuration, and only data I/O pins DQ0–DQ7 are
active and controlled by CE# and OE#. The data I/O
pins DQ8–DQ14 are tri-stated, and the DQ15 pin is
used as an input for the LSB (A-1) address function.
Requirements for Reading Array Data
To read array data from the outputs, the system must
drive the CE# and OE# pins to V . CE# is the power
IL
8
Am29SL400D
Rev. A Amend. +1 April 13, 2005
AMD [ AMD ]
