Rainbow Electronics ATAR862-8 - Manual (Page 92)

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ATAR862-8
4589B–4BMCU–02/03
Write Operations The EEPROM permits 8-bit and 16-bit write operations. A write access starts with the
START condition followed by a write control byte and one or two data bytes from the
master. It is completed via the STOP condition from the master after the acknowledge
cycle.
The programming cycle consists of an erase cycle (write "zeros") and the write cycle
(write "ones"). Both cycles together take about 10 ms.
Acknowledge Polling If the EEPROM is busy with an internal write cycle, all inputs are disabled and the
EEPROM will not acknowledge until the write cycle is finished. This can be used to
detect the end of the write cycle. The master must perform acknowledge polling by
sending a start condition followed by the control byte. If the device is still busy with the
write cycle, it will not return an acknowledge and the master has to generate a stop con-
dition or perform further acknowledge polling sequences. If the cycle is complete, it
returns an acknowledge and the master can proceed with the next read or write cycle.
Write One Data Byte
Write Two Data Bytes
Write Control Byte Only
Write Control Bytes
A -> acknowledge; HB -> high byte; LB -> low byte; R -> row address
Read Operations The EEPROM allows byte-, word- and current address read operations. The read oper-
ations are initiated in the same way as write operations. Every read access is initiated by
sending the START condition followed by the control byte which contains the address
and the read mode. When the device has received a read command, it returns an
acknowledge, loads the addressed word into the read/write buffer and sends the
selected data byte to the master. The master has to acknowledge the received byte if it
wants to proceed the read operation. If two bytes are read out from the buffer the device
increments respectively decrements the word address automatically and loads the
buffer with the next word. The read mode bits determines if the low or high byte is read
first from the buffer and if the word address is incremented or decremented for the next
Start Control byte A Data byte 1 A Stop
Start Control byte A Data byte 1 A Data byte 2 A Stop
Start Control byte A Stop
MSB LSB
Write low byte first A4 A3 A2 A1 A0 C1 C0 R/NW
Row address 0 1 0
Byte order LB(R) HB(R)
MSB LSB
Write high byte first A4 A3 A2 A1 A0 C1 C0 R/NW
Row address 1 0 0
Byte order HB(R) LB(R)