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October 2, 2003
Am29PL320D
9
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 it-
self does not occupy any addressable memory
location. The register is composed of latches that store
the commands, along with the address and data infor-
mation needed to execute the command. The contents
of the register serve as inputs to the internal state ma-
chine. The state machine outputs dictate the function
of the device. Table 1 lists the device bus operations,
the inputs and control levels they require, and the re-
sulting output. The following subsections describe
each of these operations in further detail.
Table 1.
Am29PL320D Device Bus Operations
Legend:
L = Logic Low = V
IL
, H = Logic High = V
IH
, V
ID
= 12.0
±
0.5 V, X = Don’t Care, A
IN
= Address In, D
IN
= Data In, D
OUT
= Data Out
Notes:
1. Addresses are A19–A0 in double word mode (WORD# = V
IH
), A19–A-1 in word mode (WORD# = V
IL
).
2. The sector protect and sector unprotect functions must be implemented via programming equipment. See the “Sector
Protection/Unprotection” section.
Word/Double Word Configuration
The WORD# input controls whether the device data
I/Os DQ31–DQ0 operate in the word or double word
configuration. If the WORD# input is set at V
IH
, the de-
vice is in double word configuration; DQ31–DQ0 are
active and controlled by CE# and OE#.
If the WORD# input is set at logic ‘0’, the device is in
word configuration, and only data I/Os DQ15–DQ0 are
active and controlled by CE# and OE#. The data I/Os
DQ30–DQ16 are tri-stated, and the DQ31 input 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# inputs to V
IL
. CE# is the power
control and selects the device. OE# is the output control
and gates array data to the output inputs. WE# should
remain at V
IH
. The WORD# input determines whether
the device outputs array data in words or bytes.
The internal state machine is set for reading array data
upon device power-up. 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.
See “Reading Array Data” for more information. Refer
to the AC Read Operations table for timing specifica-
tions and to Figure 13 for the timing diagram. I
CC1
in
the DC Characteristics table represents the active cur-
rent specification for reading array data.
Read Mode
Random Read (Non-Page Mode Read)
The device has two control functions which must be
satisfied in order to obtain data at the outputs. CE# is
the power control and should be used for device selec-
tion. OE# is the output control and should be used to
gate data to the output inputs if the device is selected.
Address access time (t
ACC
) is equal to the delay from
stable addresses to valid output data. The chip enable
access time (t
CE
) is the delay from the stable ad-
dresses and stable CE# to valid data at the output
inputs. The output enable access time is the delay
from the falling edge of OE# to valid data at the output
inputs (assuming the addresses have been stable for
at least t
ACC
–t
OE
time).
Operation
CE#
L
L
V
CC
±
0.3 V
L
OE#
L
H
WE#
H
L
WP#
X
X
Addresses
(Note 1)
A
IN
A
IN
DQ7–
DQ0
D
OUT
D
IN
DQ31–DQ8
WORD#
= V
IH
D
OUT
D
IN
WORD#
= V
IL
Read
Write
DQ30–DQ16 = High-Z,
DQ31 = A-1
Standby
X
X
X
X
High-Z
High-Z
High-Z
Output Disable
H
H
X
X
High-Z
High-Z
High-Z