Kramer Electronics VP-31 - Manual (Page 22)

PROTOCOL USED FOR THE VP-61RS COMMUNICATION
The protocol used for communication between the PC and the VP-61RS is defined below. The rate of data is
9600 baud with no parity, 8 data bits and one stop bit. To work at 1200 baud, DIP switch number 5 should be
set to "OFF".
N7 N6 N5 N4 N3 N2 N1 N0
MSB LSB
Detailed Description
N7 Used for communication between the Slave and the Master only and is
always "0" for communication with the PC
N6N5N4 is the binary value of the machine we are addressing minus one, e.g., if
we wish to address the Master (machine 1 by definition), then N6N5N4
= 000, if we wish to address machine 6, then N6N5N4 = 101.
N3N2N1N0 is the binary value of the input to be selected, i.e. N3N2N1N0 = 0110
is equivalent to pressing switch No. 6 of the machine.
Several special codes are also valid:
N3N2N1N0 1101 requests that the Machine being addressed sends its present status
to the PC, i.e. which input is selected on its front panel.
N3N2N1N0 1110 is an "OK" handshake, i.e. confirmation that the instruction was
received by the addressed Machine. (If the addressed machine is not
present, then this confirmation is not sent to the PC).
Information sent from the Master to the PC is done using the same format:
0 Machine number-1 New switch status
N7 N6N5N4 N3N2N1N0