Specifications

1070 072 131-102 (96.08) GB
BUEP64 Protocol 9-13
9.6 RECEIVE Connection Sequence
If there is no centralised job, the Transfer Routine remains in an idle sta-
te. If an STX is now received from the peripheral, a response can be im-
plemented with DLE, i.e., ready-to-receive state is displayed if the
Receive buffer is empty.
(All other characters have an NAK as a consequence and the Transfer
Routine remains in an idle state).
If the buffer is not ready, another check is implemented after approx. 400
ms to determine whether the buffer is now empty (ADT = max. 550 ms).
If the buffer is still not ready, the connection setup fails. An NAK is trans-
mitted.
The following receive characters are written to the buffer. The character
delay time CDT is restarted after each received character. If the CDT
elapses without another character being received, NAK is transmitted to
the peripheral.
A DLE doubling is recognised as data and the block checksum is gene-
rated. A DLE doubling is simply accepted as user data.
When the character sequence DLE, ETX and BCC has been recognised,
the Transfer Routine ends the Receive process and transmits DLE for a
correctly received block or an NAK for an incorrectly received block.
If transmission faults occurred during the Receive process, the Receive
process is continued until connection release occurs (DEL, ETX, BCC)
and NAK is transmitted. A repeat of the block is expected.
If a new transfer is not started within a block wait time of 4 s, or the Re-
ceive process was not successful after a total of six attempts, the Trans-
fer Routine aborts the Receive process and signals a fault to the PLC.