SAB82538 Datasheet, PDF (58/253 Pages) Infineon Technologies AG – ICs for Communications

SAB 82538
SAF 82538
Transmission of Frames
The ESCC8 autonomously transmits S commands and S responses in the auto mode.
Either transparent or I-frames can be transmitted by the user. The software timer has to
be operated in the internal timer mode to transmit I-frames. After the frame has been
transmitted, the timer is self-started, the XFIFO is inhibited, and the ESCC8 waits for the
arrival of a positive acknowledgement. This acknowledgement can be provided by
means of an S- or I-frame.
If no positive acknowledgment is received during time t1, the ESCC8 transmits an S
command (p = 1), which must be answered by an S response (f = 1). If the S response
is not received, the process is performed n1 times (in HDLC known as N2, refer to
register TIMR).
Upon the arrival of an acknowledgement or after the completion of this poll procedure
the XFIFO is enabled and an interrupt is generated. Interrupts may be triggered by the
following:
q Message has been positively acknowledged (ALLS interrupt)
q Message must be repeated (XMR interrupt)
q Response has not been received (TIN interrupt)
Additionally, XPR interrupts are generated which indicate that new data can be written
to the XFIFO. Using XPR enables high data rates, e.g. in conjunction with back-to-back
frames or shared flags.
In auto-mode, however, only when the ALLS interrupt has been issued may data
of a new frame be written to the XFIFO!
Upon arrival of an RNR frame, the software timer is started and the status of the remote
station is polled periodically after expiration of t1, until the status “receive ready” has
been detected. The user is informed via the appropriate interrupt. If no response is
received after n1 times, a TIN interrupt, and t1 clock periods thereafter an ALLS interrupt
is generated and the process is terminated.
Note: The internal timer mode should only be used in the auto mode.
Transparent frames can be transmitted in all operating modes. After the transmission of
a transparent frame the XFIFO is immediately released, which is confirmed by interrupt
(XPR). In this case, time monitoring can be performed with the timer in the external timer
mode.
Semiconductor Group
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