ComRead.About sys_readcom and sys

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

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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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