User Manual

92
ATAR862-3
4556B–4BMCU–02/03
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 read access. If the mem-
ory address limit is 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.
Read One Data Byte
Read Two Data Bytes
Read n Data Bytes
Read Control Bytes
A -> acknowledge, N -> no acknowledge; HB -> high byte; LB -> low byte,
R -> row address
Initialization After a
Reset Condition
The EEPROM with the serial interface has its own reset circuitry. In systems with micro-
controllers that have their own reset circuitry for power-on reset, watchdog reset or
brown-out reset, it may be necessary to bring the U505M into a known state indepen-
dent of its internal reset. This is performed by writing:
to the serial interface. If the U505M acknowledges this sequence it is in a defined state.
Maybe it is necessary to perform this sequence twice.
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
MSB LSB
Read low byte first,
address increment
A4 A3 A2 A1 A0 C1 C0 R/NW
Row address 0 1 1
Byte order LB(R) HB(R) LB(R+1) HB(R+1) - - - LB(R+n) HB(R+n)
MSB LSB
Read high byte first,
address decrement
A4 A3 A2 A1 A0 C1 C0 R/NW
Row address 1 0 1
Byte order HB(R) LB(R) HB(R-1) LB(R-1) - - - HB(R-n) LB(R-n)
Start Control byte A Data byte 1 N Stop