EUCHNER CIS3A-Mini - Manual (Page 9)

EUCHNER Identsystem CIS3A-Mini
084727-01-02/03 Subject to technical modification Page 9 / 22
With the 3964R transfer protocol, a block check character (BCC for short) is transmitted
for data integrity at the end of each data block. The block check character BCC is the even
longitudinal parity (exoring of all data bytes) of a transmitted or received block.
Generation starts with the first user data byte (first byte of the telegram) after connection
set-up and ends after characters DLE and ETX on connection clear down.
3.2.2.1 Control sends [1]
The control sends the control character STX in order to set up the connection. If the
peripheral responds before expiry of the acknowledgement delay time (QVZ, typically: 2
seconds) with control character DLE, the control system switches to transmit mode. If the
peripheral responds with control character NAK or any other character (apart from DLE) or if
the acknowledgement delay time elapses with no response, this means that connection set-
up has failed. The procedure is aborted after a total of 6 unsuccessful attempts (specification
of the 3964R protocol). If connection set-up is successful, the user information characters
contained in the control's transmit buffer are transmitted to the peripheral at the selected
transfer speed. The peripheral monitors the interval between the incoming characters. The
interval between two characters may not exceed the character delay time (ZVZ, typically: 100
ms).
Each control character DLE (10
hex
) contained in the user information must be transmitted
twice so that the communication partner recognises that the data is user data and not the
control character DLE. (DLE doubling).
After transmission of the user data, the control appends the following characters as end
identifier: DLE, ETX, BCC
The control then waits for an acknowledgement character from the peripheral. If the
peripheral sends control character DLE within the acknowledgement delay time (QVZ,
typically: 2 seconds), the data block has been accepted error-free. By contrast, if the
peripheral responds with control character NAK or any other character or if the
acknowledgement delay time elapses with no response, the control starts transmission again
with connection set-up STX. The procedure is aborted and the control sends the control
character NAK to the peripheral after a total of 6 unsuccessful attempts (specification of the
3964R protocol).
If the peripheral sends control character NAK during a running transmission, the control
aborts the block and repeats it in the manner described above. In the case of any other
character, the control initially waits for the character delay time (ZVZ) to elapse and then
sends control character NAK in order to set the peripheral to idle state. The control then
starts transmission again with connection set up STX.