Communications Protocol With Block Check Character; Block Check Character (Bcc) - HEIDENHAIN iTNC 530 HSCI Technical Manual

10.8.3 Communications protocol with block check character

Header
Block Check
Character (BCC)
1910
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:
FE1 mode

EXT1/EXT2/EXT3/EXT4 mode if MP5030.x = 1

The data transfer protocol is identical for all these modes except for the FE1
mode. In FE1 mode, a command sequence is output at the beginning to
request the contents directory from the peripheral device. For the FE1 mode,
bit 1 of MP5020.x must be set to 1.
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 plain-
language text (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.
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
HEIDENHAIN Technical Manual iTNC 530 HSCI
Bit 1 Bit 0
0 1
0 0
0 1
0 1
0 1
1 1
1 1