RS-232 / RS-485 Communication Protocol
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12 RS-232 / RS-485 Communication Protocol
This RS-232 / RS-485 communication protocol uses four bytes of information
as defined below. For RS-232, a null-modem connection between the machine
and controller is used. The default data rate is 9600 baud, with no parity, 8
data bits and 1 stop bit.
Table 10: Protocol Definitions
MSB
LSB
DESTINATION
INSTRUCTION
0
D
N5
N4
N3
N2
N1
N0
7
6
5
4
3
2
1
0
1st byte
INPUT
1
I6
I5
I4
I3
I2
I1
I0
7
6
5
4
3
2
1
0
2nd byte
OUTPUT
1
O6
O5
O4
O3
O2
O1
O0
7
6
5
4
3
2
1
0
3rd byte
MACHINE NUMBER
1
OVR
X
M4
M3
M2
M1
M0
7
6
5
4
3
2
1
0
4th byte
1st BYTE: Bit 7 – Defined as 0.
D – “ DESTINATION” :
0 - for sending information to the switchers (from the PC);
1 - for sending to the PC (from the switcher).
N5…N0 – “ INSTRUCTION”
The function that is to be performed by the switcher(s) is defined by the INSTRUCTION (6 bits). Similarly, if a function is
performed via the machine’s keyboard, then these bits are set with the INSTRUCTION NO., which was performed. The
instruction codes are defined according to the table below (INSTRUCTION NO. is the value to be set for N5…N0).
2nd BYTE: Bit 7 – Defined as 1.
I6…I0 – “ INPUT” .
When switching (ie. instruction codes 1 and 2), the INPUT (7 bits) is set as the input number which is to be switched.
Similarly, if switching is done via the machine’s front-panel, then these bits are set with the INPUT NUMBER which was
switched. For other operations, these bits are defined according to the table.
3rd BYTE: Bit 7 – Defined as 1.
O6…O0 – “ OUTPUT” .
When switching (i.e. instruction codes 1 and 2), the OUTPUT (7 bits) is set as the output number which is to be switched.
Similarly, if switching is done via the machine’s front-panel, then these bits are set with the OUTPUT NUMBER which was
switched. For other operations, these bits are defined according to the table.
4th BYTE: Bit 7 – Defined as 1.
Bit 5 – Don’t care.
OVR – Machine number override.
M4…M0 – MACHINE NUMBER.
Used to address machines in a system via their machine numbers. When several machines are controlled from a single serial
port, they are usually configured together with each machine having an individual machine number. If the OVR bit is set, then
all machine numbers will accept (implement) the command, and the addressed machine will reply. For a single machine
controlled via the serial port, always set M4…M0 = 1, and make sure that the machine itself is configured as MACHINE
NUMBER = 1.
Summary of Contents for OMX-SW5x5
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