Edwards STP-iX455, Instruction Manual

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STP-iX455/iXL455 Series Instruction Manual
9-12
O
pe
ra
tio
n
Transmission frame when data is transmitted at one block and returned at two blocks:
Designate a query command on the PC.
←
Less than 256 chr.
→
PC
→
SIM Stx 0
0 1 ? 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.
Next, the preceding SIM->PC character is "Ack", the instructed query command is
executed and the SIM returns the following response (1st block).
PC
→
SIM
Ack or Nak
SIM
→
PC Stx 0
0 1 Sp CHR C
1
C
253
Etb LRC
Then, "Ack" is sent by the SIM->PC character in reaction to the response (1st block)
from the SIM, the SIM returns the following response (2nd block).
PC
→
SIM
Ack or Nak
SIM
→
PC Stx 0
0 2 C
254
C
n
Etx LRC
The PC transmits "Ack" or "Nak"; then transmits the next command if necessary.
9.3.5 Transmission Data Format
Data value is always 16 bits signed hexadecimal value coded ASCII text.
Example: 12090 on a decimal basis equals to 2F3A on a hexadecimal basis.
9.3.6 Frame Control (Checksum)
The transmission frame is controlled by the odd number parity check.
First initialize LRC as FF
hex
. Next calculate LRC by EXCLUSIVE-OR (XOR) of all the
frame bytes containing "Stx", "Etb", "Etx" and LRC, and transmit the result as LRC.
Examples: Character string for calculation before calculating LRC
ASCII Stx 0 0 1 # Etx LRC
HEX 02 30 30 31 23 03 FF
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
Character string for transmission after calculating LRC
ASCII Stx 0 0 1 # Etx LRC
HEX 02 30 30 31 23 03 EC
However, when the MSB (most significant bit) is always 0 when data length is 7 bits, LRC is
set to 6Chex.