Edwards SCU-1600

SCU-1600 Control Unit for Turbomolecular Pump
March 10 71 Issue 1-a
5
SERIAL COMMUNICATION PROTOCOL
Transmission frame when a message exceeds 255 characters (n = 255, m<=255, k = the number of
transmission blocks):
First 1 2 3 4 5
5+n 5+n+1 5+n+2
Block ASCII Stx 0 0 1 C1
1
C1
n
Etb LRC
Second 1 2 3 4 5 5+n 5+n+1 5+n+2
Block ASCII Stx 0 0 2 C2
1
C2
n
Etb LRC
Final 1 2 3 4 5 5+m 5+m+1 5+m+2
Block ASCII Stx k Ck
1
Ck
m
Etx LRC
"Stx" is used as a start character of each transmission block; "Etb" is used as an end character of the
transmission block with a message of 255 characters; "Etx" is used as an end character of the final
transmission block (the end character of the transmission frame).
5.3.3 Control command (in the RS232/RS485 single point connection)
A control command is used when transmitting a pump operation command and a setting change
command to the SIM. The first character of the control command in the RS232/RS485 single point
connection is "Bsp" (a space character, HEX code "20") and succeeding characters are ASCII
characters corresponding to the respective function code and parameter.
Bsp CHR C
1
C
2
C
n
CHR: Function code character, C
1
to C
n
: Parameter.
Parameter (from C
1
to C
n
) serves as 16 bits signed hexadecimal value coded ASCII text. When a
message (a space character, a function code, and parameter) exceeds 255 characters, input "Bsp"
and CHR to the top transmission block only (the first transmission block of the transmission frame). It
is not necessary to input them to the second and succeeding transmission blocks.
The SIM returns the acknowledgment response character "#" when the control command is
processed normally. If not, the SIM returns the non-acknowledgment response character "!" and 3
characters of the non-acknowledgment code are added to "!".
Transmission frame when data is transmitted to one block (a message is less than 256 characters):
Designate the control command on the PC.
<- Less than 256 chr. ->
PC->SIM
Stx 0 0 1 Bsp CHR C
1
C
n
Etx LRC
SIM->PC
Ack or Nak
Always assign less than 254 characters (n< 254) to the parameter so that the message is less than
256 characters.