Accu-Sort 10, Operation And Maintenance Manual

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A-8 M
ODEL
10 O
PERATIONS AND
M
AINTENANCE
M
ANUAL
Accu-Sort Systems
If no data is available:
STX, unit id, 0, 5, lrc, CR
Example: STX 0 1 0 5 0 4 CR
HEX: 02h 30h 31h 30h 35h 30h 34h 0Dh
It is normally faster to allow the master to time out (which takes three character
times) than to use the "no data" response.
3. MUX acknowledges data in the following format:
STX, unit id, 0, 3, lrc, CR
Example:
STX 0 1 0 3 0 2 CR
HEX: 02h 30h 31h 30h 31h 30h 32h 0Dh
4. MUX polls the next unit . . .
P
ROTOCOLS
U
SED
W
ITH
RS232, C
URRENT
L
OOP
,
AND
422
RTS/CTS (Used with only RS232)
This protocol stands for "Request To Send" and "Clear To Send". This is a common
type of "handshaking" that goes on between two units. When one device wants to
transmit to another device, it will drive the RTS line indicating it has data to transmit.
When the receiving device is ready to receive, it will drive the CTS line indicating it is
ready. When you use RTS/CTS it requires the addition of two more wires on the
communication cable. If they are not needed then it is advised not to use any other
additional lines in the cable.
ACK/NAK
This is a software protocol. When a unit receives a message, it indicates whether it has
received that message correctly. If all information is received, the unit will transmit an
"ACK" (acknowledge). The ACK is a signal that more information may be transmitted. If
the information is not received correctly, then it will transmit a "NAK" (non-
acknowledge). The NAK is a signal requesting a message be retransmitted. Most
software has a limit to the number of retransmits. Three NAKS is common.
XON/XOFF
This is a software protocol. XON stands for "transmit on" and XOFF stands for
"transmit off". A unit receiving data may signal the unit transmitting that it should stop
sending data by transmitting and XOFF (ctrl-S). An XON (ctrl-Q) signals the original
unit to begin transmitting again.