CAT1021 datasheet(12/21 Pages) CATALYST

12 / 21 page

CAT1021, CAT1022, CAT1023

Doc. No. MD-3009 Rev. M

Characteristics subject to change without notice

Acknowledge Polling

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.

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.

READ OPERATIONS

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.

Figure 10. Immediate Address Read Timing

SCL

SDA

8TH BI T

STOP

NO ACK

DATA OUT

SLAVE

ADDRESS

DATA

BUS ACTIVIT Y:

MASTER

SDA LINE

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