7 Write Operations

All write operations for the AT34C04 begin with the master sending a Start condition, followed by a device address byte with the R/W bit set to logic ‘0’, and then by the word address byte. The data value(s) to be written to the device immediately follow the word address byte.

Note: All byte write and page write operations should be preceded by the SPA and or RPA commands to ensure the internal address counter is located in the desired half of the memory.

If a byte write or page write operation is attempted to a protected quadrant, the AT34C04 will respond (ACK or NACK) to the write operation according to Table 7-1.

Table 7-1. Acknowledge Status When Writing Data or Defining Write Protection
Quadrant Status	Instruction	ACK	Word Address	ACK	Data Word	ACK	Write Cycle
Write Protected with Set RSWP	Set RSWP	NACK	Don’t Care	NACK	Don’t Care	NACK	No
	Clear RSWP	ACK	Don’t Care	ACK	Don’t Care	ACK	Yes
	Byte Write or Page Write to Protected Quadrant	ACK	Word Address	ACK	Data	NACK	No
Not Protected	Set RSWP or Clear RSWP	ACK	Don’t Care	ACK	Don’t Care	ACK	Yes
Not Protected	Byte Write or Page Write	ACK	Word Address	ACK	Data	ACK	Yes