Atmely na jednom seriaku

Miroslav Sinko sinkomiro
Středa Březen 17 14:23:27 CET 2004

A standardna multiprocesorova funkcnost seriakov v 51 by nestacila?
Dufam, ze anglictina nevadi:

Multiprocessor Communications: Modes 2 and 3 have a special provision
for multiprocessor communications. In these modes, 9 data bits are
received. The 9th one goes into RB8. Then comes a stop bit. The port
can be programmed such that when the stop bit is received, the serial
port interrupt will be activated only if RB8=1. This feature is enabled
by setting bit SM2 in SCON. A way to use this feature in multiprocessor
systems is as follows:
When the master processor wants to transmit a block of data to one of
several slaves, it first sends out an address byte which identifies the
target slave. An address byte differs from a data byte in that the 9th
bit is 1 in an address byte and 0 in a data byte. With SM2=1, no slave
will be interrupted by a data byte. An address byte, however, will
interrupt all slaves, so that each slave can examine the received byte
and see if it is being addressed. The addressed slave will clear its
SM2 bit and preparate to receive the data bytes that will be coming.
The slaves that weren't being addressed leave their SM2s set and go on
about their business, ignoring the coming data bytes.

SM2 has no effect in Mode 0, and in Mode 1 can be used to check the
validity of the stop bit. In a Mode 1 reception, if SM2=1, the receive
interrupt will not be activated unless a valid stop bit is received.

Philips Data Handbook IC20


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