
10
Am29F032B
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 location.
The register is composed of latches that store the com-
mands, along with the address and data information
needed to execute the command. The contents of the
register serve as inputs to the internal state machine.
The state machine outputs dictate the function of the
device. The appropriate device bus operations table
lists the inputs and control levels required, and the re-
sulting output. The following subsections describe
each of these operations in further detail.
Table 1. Am29F032B Device Bus Operations
Legend:
L = Logic Low = VIL, H = Logic High = VIH, VID = 12.0 ± 0.5 V, X = Don’t Care, DIN = Data In, DOUT = Data Out, AIN = Address In
Note: See the sections Sector Group Protection and Temporary Sector Unprotect for more information.
Requirements for Reading Array Data
To read array data from the outputs, the system must
drive the CE# and OE# pins to VIL. CE# is the power
control and selects the device. OE# is the output con-
trol and gates array data to the output pins. WE#
should remain at VIH.
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 com-
mand 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.
See “Reading Array Data” on page 13 for more infor-
mation. Refer to the AC Read Operations table for tim-
ing specifications and to Figure 9, on page 25 for the
timing waveforms. ICC1 in the DC Characteristics table
represents the active current specification for reading
array data.
Writing Commands/Command Sequences
To write a command or command sequence (which in-
cludes programming data to the device and erasing
sectors of memory), the system must drive WE# and
CE# to VIL, and OE# to VIH.
An erase operation can erase one sector, multiple sec-
tors, or the entire device. The Sector Address Tables
indicate the address space that each sector occupies.
A “sector address” consists of the address bits re-
quired to uniquely select a sector. See the “Writing
specific address and data commands or sequences
into the command register initiates device operations.
The Command Definitions table defines the valid reg-
ister command sequences. Writing incorrect address
and data values or writing them in the improper se-
quence resets the device to reading array data.” sec-
tion for details on erasing a sector or the entire chip, or
suspending/resuming the erase operation.
After the system writes the autoselect command se-
quence, the device enters the autoselect mode. The
system can then read autoselect codes from the inter-
nal register (which is separate from the memory array)
on DQ7–DQ0. Standard read cycle timings apply in
this mode. Refer to the “Autoselect Mode” on page 11
and “Autoselect Command Sequence” on page 14
sections for more information.
ICC2 in the “DC Characteristics” on page 23 table rep-
resents the active current specification for the write
mode. The ““AC Characteristics” on page 25 section
Operation
CE#
OE#
WE#
RESET#
A0–A21
DQ0–DQ7
Read
L
H
AIN
DOUT
Write
L
H
L
H
AIN
DIN
CMOS Standby
VCC ± 0.5 V
X
VCC ± 0.5 V
X
High-Z
TTL Standby
H
X
H
X
High-Z
Output Disable
L
H
X
High-Z
Hardware Reset
X
L
X
High-Z
Temporary Sector Unprotect
(See Note)
X
VID
AIN
DIN