Read one data byte, Read two data bytes, Read n data bytes – Rainbow Electronics ATAR862-3 User Manual
Page 92: Read control bytes, Initialization after a reset condition, Atar862-3
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