CAT1021, CAT1022, CAT1023
Acknowledge Polling
READ OPERATIONS
Disabling of the inputs can be used to take
advantage of the typical write cycle time. Once the
stop condition is issued to indicate the end of the
host’s write opration, the CAT1021/22/23 initiates
the internal write cycle. ACK polling can be initiated
immediately. This involves issuing the start condition
followed by the slave address for a write operation. If
the device is still busy with the write operation, no
ACK will be returned. If a write operation has
completed, an ACK will be returned and the host can
then proceed with the next read or write operation.
The READ operation for the CAT1021/22/23 is initiated in
the same manner as the write operation with one
¯¯
exception, the R/W bit is set to one. Three different READ
operations are possible: Immediate/Current Address
READ, Selective/Random READ and Sequential READ.
WRITE PROTECTION PIN (WP)
The Write Protection feature (CAT1021 only) allows
the user to protect against inadvertent memory array
programming. If the WP pin is tied to VCC, the entire
memory array is protected and becomes read only.
The CAT1021 will accept both slave and byte addre-
sses, but the memory location accessed is protected
from programming by the device’s failure to send an
acknowledge after the first byte of data is received.
Figure 10. Immediate Address Read Timing
S
T
A
R
T
S
T
O
P
BUS ACTIVIT Y:
MASTER
SLAVE
ADDRESS
SDA LINE
S
P
A
C
K
N
O
DATA
A
C
K
SCL
SDA
8
9
8TH BIT
DATA OUT
NO ACK
STOP
Doc. No. 3009 Rev. L
12
© 2007 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
CATALYST [ CATALYST SEMICONDUCTOR ]
