Edwards STP-iXA4507 Series User Manual

STP-iXA4507 series Turbomolecular Pump
MT-91E-001-0
Page 73
SERIAL COMMUNICATION PROTOCOL
5
5.3.5 Transmission data format
The data value is 16 bit signed hexadecimal value coded ASCII text.
Example: 12090 on decimal equals 2F3A on hexadecimal.
5.3.6 Frame control (checksum)
The transmission frame is controlled by the odd number parity check. First, LRC is initialized to FF
hex
.
Next, LRC is calculated by EXCLUSIVE-OR (XOR) of all the frame bytes containing "Stx", "Etb",
"Etx" and LRC and transmitted as LRC.
Examples:
A character string for calculation before the calculating LRC:
ASCII
Stx
0
0
1
#
Etx
LRC
HEX
02
30
30
31
23
03
FF
The calculation of LRC:
02
hex
XOR 30
hex
XOR 30
hex
XOR 31
hex
XOR 23
hex
XOR 03
hex
XOR FF
hex
= EC
hex
The character string for transmission after the calculating LRC:
ASCII
Stx
0
0
1
#
Etx
LRC
HEX
02
30
30
31
23
03
EC
However, LRC is set to 6C
hex
if the data length is 7 bits in the above example since the MSB (most
significant bit) is always 0.
5.3.7 Error control
• Transmit the transmission frame repeatedly from a PC when a SIM transmits "Nak" (parity check
error). On the other hand, when a SIM receives "Nak" from a PC, the transmission frame is
transmitted again. This operation is repeated up to 5 times.
• A SIM transmits "Ack" or "Nak" to a PC after receiving a communication command. When the PC
cannot receive "Ack" or "NaK" after 2 seconds, retransmit the transmission frame from the PC.
When these communication errors repeatedly occur, display an error message or start the error
routine on the PC.
5.3.8 Transmission frame in RS485 multi-point connection
In an RS485 multi-point connection, a network frame ID character, "@", and 3 characters as a
network frame number are added to a transmission frame to recognize a network frame and have
compatibility for the standard transmission frame of RS485.

Edwards STP-iXA4507 Series Specifications

General

Brand	Edwards
Model	STP-iXA4507 Series
Category	Water Pump
Language	English