Product : ISaGRAF V3
Date : 01-August-1996
File : ComRead.About sys_readcom and sys_readbcom.htm
Subject : About sys_readcom and sys_readbcom
Keywords: sys_readcom - sys_readbcom - system layer - communication
The ISaGRAF kernel makes sequential access to system layer to
get bytes from the communication. This can also be used in the
case of a packet based protocol. It means:
- the whole packet is sent to the target
- the received packet must be stored in the system layer
- sys_readcom and sys_readbcom make only sequential reading of
the packet (no more exchange on the line).
Remember that ISaGRAF implements a master/slave protocol based
on question & answer mechanism. This implies that:
- no other question is sent by the debugger until the target
answers to the current one
- the only things required to implement sequential reading of
the received packet are the current read pointer in the
packet and a "packet is here" information.
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