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AM29F160D View Datasheet(PDF) - Advanced Micro Devices

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AM29F160D Datasheet PDF : 46 Pages
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Autoselect Command Sequence
The autoselect command sequence allows the host
system to access the manufacturer and devices codes,
and determine whether or not a sector is protected.
The Command Definitions table shows the address
and data requirements. This method is an alternative to
that shown in the Autoselect Codes (High Voltage
Method) table, which is intended for PROM program-
mers and requires VID on address bit A9.
The autoselect command sequence is initiated by
writing two unlock cycles, followed by the autoselect
command. The device then enters the autoselect
mode, and the system may read at any address any
number of times, without initiating another command
sequence.
A read cycle at address XX00h retrieves the manufac-
turer code. A read cycle at address XX01h in word
mode (or 02h in byte mode) returns the device code.
A read cycle containing a sector address (SA) and the
address 02h in word mode (or 04h in byte mode) re-
turns 01h if that sector is protected, or 00h if it is un-
protected. Refer to the Sector Address tables for valid
sector addresses. When a read occurs at an address
within the 16 Kbyte boot sector (SA34 for top boot de-
vices and SA0 for bottom boot devices), the input on
WP# may determine what code will be returned.
16Kb Sector
Protection
WP#
input
Autoselect
Code
protected
VIH
protected
VIL
unprotected
VIH
unprotected
VIL
01 (protected)
01 (protected)
00 (unprotected)
01 (protected)
The system must write the reset command to exit the
autoselect mode and return to reading array data.
Word/Byte Program Command Sequence
The system may program the device by byte or word,
on depending on the state of the BYTE# pin. Program-
ming is a four-bus-cycle operation. The program com-
mand sequence is initiated by writing two unlock write
cycles, followed by the program set-up command. The
program address and data are written next, which in
turn initiate the Embedded Program algorithm. The
system is not required to provide further controls or tim-
ings. The device automatically provides internally gen-
erated program pulses and verify the programmed cell
margin. The Command Definitions take shows the ad-
dress and data requirements for the byte program com-
mand sequence.
When the Embedded Program algorithm is complete,
the device then returns to reading array data and ad-
dresses are no longer latched. The system can deter-
mine the status of the program operation by using DQ7,
DQ6, or RY/BY#. See “Write Operation Status” for in-
formation on these status bits.
Any commands written to the device during the Em-
bedded Program Algorithm are ignored. Note that a
hardware reset immediately terminates the program-
ming operation. The program command sequence
should be reinitiated once the device has reset to read-
ing array data, to ensure data integrity.
Programming is allowed in any sequence and across
sector boundaries. A bit cannot be programmed
from a “0” back to a “1”. Attempting to do so may halt
the operation and set DQ5 to “1”, or cause the Data#
Polling algorithm to indicate the operation was suc-
cessful. However, a succeeding read will show that the
data is still “0”. Only erase operations can convert a “0”
to a “1”.
Unlock Bypass Command Sequence
The unlock bypass feature allows the system to pro-
gram words to the device faster than using the stan-
dard program command sequence. The unlock bypass
command sequence is initiated by first writing two un-
lock cycles. This is followed by a third write cycle con-
taining the unlock bypass command, 20h. The device
then enters the unlock bypass mode. A two-cycle un-
lock bypass program command sequence is all that is
required to program in this mode. The first cycle in this
sequence contains the unlock bypass program com-
mand, A0h; the second cycle contains the program
address and data. Additional data is programmed in
the same manner. This mode dispenses with the initial
two unlock cycles required in the standard program
command sequence, resulting in faster total program-
ming time. Table 9 shows the requirements for the
command sequence.
During the unlock bypass mode, only the Unlock By-
pass Program and Unlock Bypass Reset commands
are valid. To exit the unlock bypass mode, the system
must issue the two-cycle unlock bypass reset com-
mand sequence. The first cycle must contain the data
90h. The second cycle must contain the data 00h. The
device then returns to the read mode.
Am29F160D
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