X68257
MODE SELECTION
CE
V
SS
LOW
HIGH
HIGH
E
X
X
HIGH
R/W
X
X
HIGH
LOW
Mode
Standby
Standby
Read
Write
I/O
High Z
High Z
D
OUT
D
IN
Power
Standby (CMOS)
Standby (TTL)
Active
Active
6539 PGM T02.2
PAGE WRITE OPERATION
Regardless of the microcontroller employed, the X68257
supports page mode write operations. This allows the
microcontroller to write from 1 to 128 bytes of data to the
X68257. Each individual write within a page write opera-
tion must conform to the byte write timing requirements.
The rising edge of E starts a timer delaying the internal
programming cycle 100µs. Therefore, each successive
write operation must begin within 100µs of the last byte
written. The following waveforms illustrate the sequence
and timing requirements.
Page Write Timing Sequence for E Controlled Operation
OPERATION
BYTE 0
BYTE 1
BYTE 2
LAST BYTE
READ (1)(2)
AFTER tWC READY FOR
NEXT WRITE OPERATION
CE
AS
A/D0–A/D7
AIN
DIN
AIN
DIN
AIN
DIN
AIN
DIN
AIN
DIN
AIN
AIN
A8–A14
An
An
An
An
An
ADDR
Next Address
E
R/W
tBLC
tWC
6539 FHD F07.1
Note:
(1) For each successive write within a page write cycle A
7
–A
14
must be the same.
4
XICOR [ XICOR INC. ]
