X4643/5 – Preliminary Information
Figure 10. Writing 12 bytes to a 64-byte page starting at location 60.
8 Bytes
Address Pointer
Ends Here
Addr =
8
4 Bytes
Address
=7
Address
60
Address
n-1
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
Byte load completed
by issuing STOP.
Enter ACK Polling
Issue START
Issue Slave Address
Byte (Read or Write)
Issue STOP
ACK
returned?
YES
NO
Nonvolatile Cycle
complete. Continue
command sequence?
NO
Issue STOP
YES
Continue Normal
Read or Write
Command Sequence
PROCEED
REV 1.26 4/30/02
www.xicor.com
Characteristics subject to change without notice.
10 of 22
XICOR [ XICOR INC. ]
