CAT1024 datasheet(13/20 Pages) CATALYST

13 / 20 page

CAT1024, CAT1025

Doc No. 3008, Rev. M

Immediate/Current Address Read

The CAT1024 and CAT1025 address counter contains

the address of the last byte accessed, incremented by

one. In other words, if the last READ or WRITE access

was to address N, the READ immediately following

would access data from address N+1. For N=E=255, the

counter will wrap around to zero and continue to clock

out valid data. After the CAT1024 and CAT1025 receives

its slave address information (with the R/

W bit set to

one), it issues an acknowledge, then transmits the 8-bit

byte requested. The master device does not send an

acknowledge, but will generate a STOP condition.

Selective/Random Read

Selective/Random READ operations allow the Master

device to select at random any memory location for a

READ operation. The Master device first performs a

‘dummy’ write operation by sending the START condition,

slave address and byte addresses of the location it

wishes to read. After the CAT1024 and CAT1025

acknowledges, the Master device sends the START

condition and the slave address again, this time with the

W bit set to one. The CAT1024 and CAT1025 then

responds with its acknowledge and sends the 8-bit byte

requested. The master device does not send an

acknowledge but will generate a STOP condition.

Sequential Read

The Sequential READ operation can be initiated by

either the Immediate Address READ or Selective READ

operations. After the CAT1024 and CAT1025 sends the

inital 8-bit byte requested, the Master will responds with

an acknowledge which tells the device it requires more

data. The CAT1024 and CAT1025 will continue to output

an 8-bit byte for each acknowledge, thus sending the

STOP condition.

The data being transmitted from the CAT1024 and

CAT1025 is sent sequentially with the data from address

N followed by data from address N+1. The READ

operation address counter increments all of the CAT1024

and CAT1025 address bits so that the entire memory

array can be read during one operation.

SLAVE

ADDRESS

BUS ACTIVITY:

MASTER

SDA LINE

BYTE

ADDRESS (n)

DATA n

SLAVE

ADDRESS

Figure 11. Selective Read Timing

BUS ACTIVITY:

MASTER

SDA LINE

DATA n+x

DATA n

DATA n+1

DATA n+2

SLAVE

ADDRESS

Figure 12. Sequential Read Timing

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