1997 Apr 02

8

Philips Semiconductors

Product specification

128

PCA8581; PCA8581C

To transmit eight bytes in sequential order, begin with the lowest address bits 0 0 0. The data is written after a stop is

(6 to 10 ms) during which the device will not respond to its slave address. Note that to write the next row, a new write

operation is required (start, slave address, row address, data and stop).

An unlimited number of data bytes can be read in one operation. The address is automatically incremented. If a read

without setting the word address is performed after a write operation, the address pointer may point at a byte in the row

after the previously written row. This occurs if, during writing, the three lowest address bits (column) rolled over.

Fig.9 Master reads after setting word address (WRITE word address; READ data).

handbook, full pagewidth

S

0A

SLAVE ADDRESS

WORD ADDRESS

A

A

SLAVE ADDRESS

acknowledgement

from slave

acknowledgement

from slave

acknowledgement

from slave

R/W

X

don't

care

acknowledgement

from master

A

DATA

auto increment

memory word address

MLB891

P

no acknowledgement

from master

1

DATA

auto increment

memory word address

last byte

R/W

S1

n bytes

at this moment master -

transmitter becomes

master - receiver and

PCA8581(C) slave - receiver

becomes slave - transmitter

Fig.10 Master reads slave immediately after first byte (READ mode).

handbook, full pagewidth

S

1A

SLAVE ADDRESS

DATA

A1

DATA

acknowledgement

from slave

acknowledgement

from slave

acknowledgement

from slave

R/W

auto increment

word address

MBD824

auto increment

word address

n bytes

last bytes

P