U3280M Datasheet, PDF (9/18 Pages) ATMEL Corporation – TRANSPONDER INTERFACE FOR MICROCONTROLLER

Read Operations
Read One Data Byte
Read Two Data Bytes
Read n Data Bytes
Read Control Bytes
U3280M
The EEPROM allows byte-, word- and current address read operations. The read oper-
ations are initiated in the same way as write operations. Each 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 to
proceed with the read operation. If two bytes are read out from the buffer, the device
automatically increments or decrements the word address and loads the buffer with the
next word. The read mode bit 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 read access.
When the memory address limit has been reached, the data word address will “roll over”
and the sequential read will continue. The master can terminate the read operation after
every byte by not responding with an acknowledge (N) and by issuing a STOP
condition.
START Control byte A Data byte 1 N STOP
START Control byte A Data byte 1 A Data byte 2 N STOP
START Control byte A Data byte 1 A Data byte 2 A - - - - - - Data byte n N STOP
A →acknowledge, N →no acknowledge
Read Low Byte First, Address Increment
MSB
A4
A3
A2
A1
A0
C1
Row address
0
LSB
C0 R/NW
1
1
Byte Order
LB(R) HB(R)
LB(R+1) HB(R+1) - - - -
LB(R+n) HB(R+n)
Read High Byte First, Address Decrement
MSB
A4
A3
A2
A1
A0
C1
Row address
1
LSB
C0 R/NW
0
1
Byte Order
HB(R) LB(R) HB(R-1) LB(R-1)
HB: high byte; LB: low byte; R: row address
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HB(R-n) LB(R-n)
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4688B–RFID–12/04