ACU-RITE MILLPWR G2, Техническое руководство

Страница: 537 / 546

7.7 Serial Data Transmission Protocols 537
7.7.2 Communications Protocol with Block Check Character
This protocol is specific to HEIDENHAIN and operates with its own control
characters and an additional data check feature when transmitting.
The protocol is active during blockwise data transfer in FE1 mode,
In the FE1 mode, a command sequence is output at the beginning to request
the contents directory from the peripheral device.
Header When a file is transferred, the first block — called the header — consists of
the following characters:
<SOH><K><Name><M><ETB><BCC><DC1>
Block Check
Character (BCC) 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 indi-
vidual 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 conver-
sational format (H), is input through the data interface (E).
A parity bit is also generated for the BCC. With even parity, the parity bit in this
example is assigned the value 1.
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
Character Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
SOH 0 0 0 0 0 0 1
H 1 0 0 1 0 0 0
1 0 1 1 0 0 0 1
5 0 1 1 0 1 0 1
E 1 0 0 0 1 0 1
ETB 0 0 1 0 1 1 1
BCC 0 0 1 1 1 1 1