Edwards SCU-1601

SCU-1601 Control Unit for Turbomolecular Pump
MT-96E-1B1-0
Page 90
5
SERIAL COMMUNICATION PROTOCOL
5.3.10 Query command in the RS485 multi-point connection
The query command to be used when a pump operation instruction or a setting change instruction is
transmitted from the SIM and is arranged in the order specified below. The top is “?” (HEX code “3F”)
and ASCII characters corresponding to the respective function code and parameter follow.
?
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 “?” 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 query 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 from one block and returned to two blocks.
Designate a query command on the PC.
<- Less than 256 chr.->
PC->SIM
@
F
1
F
2
Stx
0
0
1
?
CHR
C
1
C
n
Etx
LRC
SIM->PC
Ack or Nak
F
1
F
2
Always assign less than 254 characters (n< 254) to the parameter so that the message is less than
256 characters.
Next, the preceding SIM->PC character is “Ack”, the instructed query command is executed and the
SIM returns the following response (1
st
block).
PC->SIM
Ack or Nak
F
1
F
2
SIM->PC
@
F
1
F
2
Stx
0
0
1
Sp
CHR
C
1
C
253
Etb
LRC
Then “Ack” is sent by the PC->SIM character in reaction to the response (1
st
block) from the SIM, the
SIM returns the following response (2
nd
block).
PC->SIM
Ack or Nak
F
1
F
2
SIM->PC
@
F
1
F
2
Stx
0
0
2
C
254
C
n
Etx
LRC
The PC transmits “Ack” or “Nak”; then transmits the next command if necessary.