X24026
Page Write
Flow 1. ACK Polling Sequence
The X24026 is capable of a four byte page write opera-
tion. It is initiated in the same manner as the byte write
operation, but instead of terminating the write cycle after
the first data word is transferred, the master can transmit
up to three more words. After the receipt of each word,
the X24026 will respond with an acknowledge.
WRITE OPERATION
COMPLETED
ENTER ACK POLLING
ISSUE
START
After the receipt of each word, the two low order address
bits are internally incremented by one. The high order six
bits of the address remain constant. If the master should
transmit more than four words prior to generating the
stop condition, the address counter will “roll over” and the
previously written data will be overwritten. As with the
byte write operation, all inputs are disabled until comple-
tion of the internal write cycle. Refer to Figure 6 for the
address, acknowledge and data transfer sequence.
ISSUE SLAVE_
ADDRESS AND R/W = 0
ISSUE STOP
ACK
NO
RETURNED?
Acknowledge Polling
The disabling of the inputs, during the internal write oper-
ation, can be used to take advantage of the typical 5 ms
write cycle time. Once the stop condition is issued to indi-
cate the end of the host’s write operation the X24026 ini-
tiates the internal write cycle. ACK polling can be initiated
immediately. This involves issuing the start condition fol-
lowed by the slave address for a write operation. If the
X24026 is still busy with the write operation no ACK will
be returned. If the X24026 has completed the write oper-
ation an ACK will be returned and the master can then
proceed with the next read or write operation.
YES
NEXT
OPERATION
A WRITE?
NO
YES
ISSUE BYTE
ADDRESS
ISSUE STOP
PROCEED
READ OPERATIONS
PROCEED
Read operations are initiated in the same manner as
write operations with the exception that the R/W bit of the
slave address is set to a one. There are three basic read
operations: current address read, random read and
sequential read.
7020 FRM 09
It should be noted that the ninth clock cycle of the read
operation is not a “don’t care.” To terminate a read opera-
tion, the master must either issue a stop condition during
the ninth cycle or hold SDA HIGH during the ninth clock
cycle and then issue a stop condition.
6
XICOR [ XICOR INC. ]
