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8.4.3 Transmission Protocol with Block Check Character
Header
Block Check
Character (BCC)
December 2001
This protocol is specific to HEIDENHAIN and operates with its own control
characters and an additional data check feature when transmitting.
The protocol is set with the following operating modes:
n
FE1 mode
n
FE2 mode
n
EXT1/EXT2/EXT3 mode if MP5030.x = 1
The data transfer protocol is identical for all these modes except for the FE1
mode. In the FE1 mode, a command sequence is output at the beginning to
request the contents directory from the peripheral unit.
When a file is transferred, the first block — called the header — consists of
the following characters:
<SOH><K><Name><M><ETB><BCC><DC1>
Character
Meaning
<SOH>
Identifies the beginning of the header
<K>
File code
<Name>
File name
<M>
Data transfer mode (E = input, A = output)
<ETB>
Identifies the end of the header
<BCC>
Block Check Character
<DC1>
XON
In addition to checking the parity of the individual characters, the parity of the
complete transferred block is also checked. The BCC always rounds the
individual bits of the transferred characters in a data transfer block to even
parity.
Example of BCC generation:
In this example, program 15, which has been written in HEIDENHAIN dialog
(H), is input through the data interface (E).
Character
Bit 6
Bit 5
SOH
0
0
H
1
0
1
0
1
5
0
1
E
1
0
ETB
0
0
BCC
0
0
A parity bit is also generated for the BCC. With even parity, the parity bit in this
example is assigned the value 1.
Data Transmission Protocols
Bit 4
Bit 3
Bit 2
0
0
0
0
1
0
1
0
0
1
0
1
0
0
1
1
0
1
1
1
1
Bit 1
Bit 0
0
1
0
0
0
1
0
1
0
1
1
1
1
1
8 – 23
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