SCH2 Technical Manual TSP016.doc Issue 3.0 – January 2005
Money Controls 2005. All rights reserved.
Page 45 of 61
Header 003: Clear comms status variables
Transmitted data : <none>
Received data : ACK
Clears the counters returned by the ‘Request comms status variables’ command.
Header 002: Request comms status variables
Transmitted data : <none>
Received data : [ rx timeouts ] [ rx bytes ignored ] [ rx bad checksums ]
[ rx timeouts ]
Number of receive message timeouts recorded by the processor.
There is an inter-byte timeout value of Trxout - see Appendix B. The ccTalk protocol has a
variable length packet structure but data timeouts can be detected and counted.
[ rx bytes ignored ]
Number of receive bytes ignored by the processor ( due to receive buffer overflow ).
SCH2 has a receive buffer length of 15 bytes for the data part of the packet - the header and
checksum are stored elsewhere. Packets with more than 15 bytes of data increase the
ignored counter by the total number of data bytes. So sending a message with 20 data bytes
would increase the ignored bytes by 20. Likewise a message with 15 or less would not do
anything to the counter, a message with 16 by 16 and a message with 252 by 252.
[ rx bad checksums ]
Number of messages received by the processor with bad checksums.
) Note that if an encrypted command is sent on a multi-drop bus ( e.g. to a bill validator ) then
the hopper records this as a checksum fail as it verifies the checksum prior to an address
match, rather than afterwards.
All these counters are cumulative and wrap around to 0 after 255.
When testing a new software driver, it is worth checking these counters after a series of
message transactions to confirm all is well.
Header 001: Reset device
Transmitted data : <none>
Received data : ACK
This is the command required for a ‘software reset’.
An ACK is returned prior to resetting.
Host software should allow a delay after the ACK before sending the next command to allow
the hopper initialisation code to complete - see TSinit in Appendix B.
After a ‘Reset device’ command, various status flags are cleared (see the ‘Test hopper’
command ).
Any motor parameters sent with a ‘Modify variable set’ command will return to their default
values. Default values are given in Appendix A.
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