X4643 datasheet(10/22 Pages) XICOR

10 / 22 page

X4643/5 – Preliminary Information

Characteristics subject to change without notice.

10 of 22

REV 1.26 4/30/02

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Figure 10. Writing 12 bytes to a 64-byte page starting at location 60.

Address

4 Bytes

n-1

8 Bytes

Address

= 7

Address Pointer

Ends Here

Addr = 8

The master terminates the Data Byte loading by issuing

a stop condition, which causes the device to begin the

nonvolatile write cycle. As with the byte write operation,

all inputs are disabled until completion of the internal

write cycle. See Figure 9 for the address, acknowledge,

and data transfer sequence.

Stops and Write Modes

Stop conditions that terminate write operations must

be sent by the master after sending at least 1 full data

byte plus the subsequent ACK signal. If a stop is

issued in the middle of a data byte, or before 1 full data

byte plus its associated ACK is sent, then the device

will reset itself without performing the write. The con-

tents of the array will not be effected.

Acknowledge Polling

The disabling of the inputs during nonvolatile cycles

can be used to take advantage of the typical 5ms write

cycle time. Once the stop condition is issued to indi-

cate the end of the master’s byte load operation, the

device initiates the internal nonvolatile cycle. Acknowl-

edge polling can be initiated immediately. To do this,

the master issues a start condition followed by the

Slave Address Byte for a write or read operation. If the

device is still busy with the nonvolatile cycle then no

ACK will be returned. If the device has completed the

write operation, an ACK will be returned and the host

can then proceed with the read or write operation.

Refer to the ﬂow chart in Figure 11.

Figure 11. Acknowledge Polling Sequence

ACK

returned?

Issue Slave Address

Byte (Read or Write)

Byte load completed

by issuing STOP.

Enter ACK Polling

Issue STOP

Issue START

YES

Nonvolatile Cycle

complete. Continue

command sequence?

Issue STOP

Continue Normal

Read or Write

Command Sequence

PROCEED

YES

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