X24320PI datasheet(8/17 Pages) XICOR

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X24320

Random Read

Random read operation allows the master to access

any memory location in the array. Prior to issuing the

Slave Address Byte with the R/W bit set to one, the

master must ﬁrst perform a “Dummy” write operation.

The master issues the start condition and the Slave

Address Byte with the R/W bit low, receives an

acknowledge, then issues the Word Address Byte 1,

receives another acknowledge, then issues the Word

Address Byte 0. After the device acknowledges receipt

of the Word Address Byte 0, the master issues another

start condition and the Slave Address Byte with the

R/W bit set to one. This is followed by an acknowledge

and then eight bits of data from the device. The master

terminates the read operation by not responding with

an acknowledge and then issuing a stop condition.

Refer to ﬁgure 9 for the address, acknowledge, and

data transfer sequence.

The device will perform a similar operation called “Set

Current Address” if a stop is issued instead of the

second start shown in ﬁgure 9. The device will go into

standby mode after the stop and all bus activity will be

ignored until a start is detected. The effect of this oper-

ation is that the new address is loaded into the

address counter, but no data is output by the device.

The next Current Address Read operation will read

from the newly loaded address.

Sequential Read

Sequential reads can be initiated as either a current

address read or random read. The ﬁrst Data Byte is

transmitted as with the other modes; however, the

master now responds with an acknowledge, indicating

it requires additional data. The device continues to

output data for each acknowledge received. The

master

terminates

the

read

operation

not

responding with an acknowledge and then issuing a

stop condition.

The data output is sequential, with the data from address

n followed by the data from address n + 1. The address

counter for read operations increments through all byte

addresses, allowing the entire memory contents to be

read during one operation. At the end of the address

space the counter “rolls over” to address 0000h and the

device continues to output data for each acknowledge

received. Refer to ﬁgure 10 for the acknowledge and

data transfer sequence.

SLAVE

ADDRESS

DATA

(1)

DATA

(2)

SIGNALS

FROM THE

MASTER

SDA BUS

SIGNALS

FROM THE

SLAVE

DATA

(n–1)

DATA

(n)

(n is any integer greater than 1)

7035 FM 12

SIGNALS

FROM THE

MASTER

SDA BUS

SIGNALS

FROM THE

SLAVE

ADDRESS

WORD ADDRESS

BYTE 1

SLAVE

ADDRESS

WORD ADDRESS

BYTE 0

DATA

1 0 1 0

7035 FM 11

Figure 9. Random Read Sequence

Figure 10. Sequential Read Sequence

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