AS29LV800 ANADIGICS Inc, AS29LV800 Datasheet - Page 7

• Manufacturer Part Number: AS29LV800
• Description: 3V 1M8/512K16 CMOS Flash EEPROM
• Manufacturer: ANADIGICS Inc

October 2000
Command definitions
Item
Reset/Read
ID Read
Hardware Reset
Byte/word
Programming
DID 11-40002-A. 10/19/00
Description
Initiate read or reset operations by writing the Read/Reset command sequence into the command
register. This allows the microprocessor to retrieve data from the memory. Device remains in read
mode until command register contents are altered.
Device automatically powers up in read/reset state. This feature allows only reads, therefore
ensuring no spurious memory content alterations during power up.
AS29LV800 provides manufacturer and device codes in two ways. External PROM programmers
typically access the device codes by driving +10V on A9. AS29LV800 also contains an ID Read
command to read the device code with only +3V, since multiplexing +10V on address lines is
generally undesirable.
Initiate device ID read by writing the ID Read command sequence into the command register.
Follow with a read sequence from address XXX00h to return MFR code. Follow ID Read
command sequence with a read sequence from address XXX01h to return device code.
To verify write protect status on sectors, read address XXX02h. Sector addresses A18–A12
produce a 1 on DQ0 for protected sector and a 0 for unprotected sector.
Exit from ID read mode with Read/Reset command sequence.
Holding RESET low for 500 ns resets the device, terminating any operation in progress; data
handled in the operation is corrupted. The internal state machine resets 20 µs after RESET is
driven low. RY/BY remains low until internal state machine resets. After RESET is set high, there
is a delay of 50 ns for the device to permit read operations.
Programming the AS29LV800 is a four bus cycle operation performed on a byte-by-byte or
word-by-word basis. Two unlock write cycles precede the Program Setup command and program
data write cycle. Upon execution of the program command, no additional CPU controls or
timings are necessary. Addresses are latched on the falling edge of CE or WE, whichever is last;
data is latched on the rising edge of CE or WE, whichever is first. The AS29LV800’s automated
on-chip program algorithm provides adequate internally-generated programming pulses and
verifies the programmed cell margin.
Check programming status by sampling data on the RY/ BY pin, or either the DATA polling
(DQ7) or toggle bit (DQ6) at the program address location. The programming operation is
complete if DQ7 returns equivalent data, if DQ6 = no toggle, or if RY/BY pin = high.
The AS29LV800 ignores commands written during programming. A hardware reset occurring
during programming may corrupt the data at the programmed location.
AS29LV800 allows programming in any sequence, across any sector boundary. Changing data
from 0 to 1 requires an erase operation. Attempting to program data 0 to 1 results in either DQ5 =
1 (exceeded programming time limits); reading this data after a read/reset operation returns a 0.
When programming time limit is exceeded, DQ5 reads high, and DQ6 continues to toggle. In this
state, a Reset command returns the device to read mode.
ALLIANCE SEMICONDUCTOR
®
AS29LV800
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