HEIDENHAIN MANUALPLUS 620

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1786 HEIDENHAIN Technical Manual MANUALplus 620

At the end of every block, the receiver checks whether it has been transferred

correctly.

To do this, the receiver computes a BCC from the received block and

compares it with the received BCC. If the received BCC and the computed

BCC are identical, the receiver transmits the character <ACK> for positive

acknowledgment. If the two BCCs are not identical, the data block was not

transmitted correctly. The receiver transmits the character <NAK> for

negative acknowledgment. The block must be re-transmitted. This process is

repeated up to 15 times.

If the header is acknowledged with <ACK>, the first file block can be

transmitted:

The beginning of a file block is identified by the control character <STX>. The

remaining control characters in this block are identical with the control

characters in the header. If this block is acknowledged by <ACK>, then the

next program block is transmitted. If <NAK> is transmitted, the same block

has to be re-transmitted, etc. Once the last program block has been

acknowledged by <ACK>, the transmission is terminated by the characters

<ETX> (end of text) and <EOT> (end of transmission).

Handshaking The character <DC1> (XON) follows the BCC. This character is required by

many devices to explicitly request the transmission once again from the

transmitter.

The <DC1> character is not required for reading in a file in the BCC format.

The transmitter waits and only resumes data transmission when the receiver

has transmitted a positive (ACK) or negative (NAK) acknowledgment to

indicate that the receiving buffer is ready.

To disable transmission of the character <DC1>:

 Set MP_flowControl to NONE.

Example:

A file with the name PPP is to be transferred to a peripheral device (e.g.

HEIDENHAIN FE 401 Floppy Disk Unit).

Control to peripheral device Peripheral device to control

<SOH><L>PPP<A><ETB>BCC ACK

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HEIDENHAIN MANUALPLUS 620 - Page 1786