EUCHNER CIS3(A) - Manual (Page 8)

EUCHNER Identsystem CIS3
071652-01-8/99 Subject to technical modifications page 8 / 23
4.2.2.1 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 transfer protocol reverts 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 3964-R 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 3964-R 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.
4.2.2.2 Control receives /1/
If the control receives control character STX from the peripheral in idle state, it responds with
DLE. If the control receives another character (apart from STX) in idle state, it waits for the
character delay type (ZVZ, typically: 100 ms) to elapse and then sends the control character
NAK. After each character, the next character is awaited during the character delay time
(ZVZ). If the character delay time elapses without reception, control character NAK is sent to
the peripheral.
If the control detects character string DLE ETX BCC, it terminates reception. It compares
the received block check character BCC with the internally generated longitudinal parity. If
the block check character is correct and no other reception error has occurred, the control
sends control character DLE. If the BCC is errored, control character NAK is sent to the
peripheral. A retry is then awaited. If it is not possible to receive the block error-free even
after a total of 6 attempts (specification of the 3964-R protocol), or if the retry is not started
by the peripheral within the block waiting time of 4 seconds, the control aborts reception.
If transmission errors (lost character, frame error, parity error) occur during reception,
reception continues through to connection cleardown and control character NAK is then sent
to the peripheral. A retry in the manner described above is then awaited.