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ASM 421 Technical Description
6GT2 097-3AH00-0DA2
– 18 –
RD: 03/02
6GT2 002-0DA00
ASM 421 / V.24
Subject to change without notice!
6GT2 002-0DB00
ASM 421 / RS422
6GT2 002-0DC00
ASM 421 / TTY
J31069-D0142-U001-A0-7618
3
Programming the ASM 421 module
3.1
3964R procedure
The 3964R procedure provides secure data transmission across a point-to-point connection. Security is
achieved by transmitting the data one block at a time with parity check, block check character (BCC) and
acknowledgement of receipt. All characters from 00hex to FFhex can be present in the data block.
Character frame:
Transmission: asynchronous
Baud rate:
2400, 4800, 9600, 19200 Baud
Data bits:
8
Parity:
odd/even (switch selectable)
Stop bit:
1
1
2
3
4
5
6
7
8
P
8 data bits
Start step
Parity bit
Stop bit
Character frame 11 bits
Start step
Next
character
t
Control characters in the 3964R procedure:
Character
Code (hex)
Purpose
STX
DLE ETX
DLE
NAK
DLE DLE
02
10 03
10
15
10 10
Initialization of a transmit operation (signals ready–to–send)
Marks the end of a transmission block
Ready–to–receive (or DLE duplication in data stream)
Negative response on block–check–error or unrecognized
DLE duplication in data block; used if the value 10hex
occurs in the data stream.
start character