SAF82525 Infineon Technologies AG, SAF82525 Datasheet - Page 28

• Manufacturer Part Number: SAF82525
• Description: Data Communications ICs
• Manufacturer: Infineon Technologies AG

3
When operating in the auto-mode, the HSCX offers a high degree of procedural support. In
addition to address recognition, the HSCX autonomously processes all (numbered) S- and
I-frames (prerequisite window size 1) with either normal or extended control field format
(modulo 8 or modulo 128 sequence numbers – selectable via RAH2 register).
The following functions will be performed:
In addition, all unnumbered frames are forwarded directly to the processor.
Additional logic connections can be operated in parallel by software. The logic link can be
initialized by software at any time (RHR).
3.1 Full-Duplex LAPB/LAPD Operation
Initially (i.e. after RESET), the LAP controllers of the two serial channels are configured to
function as a combined station, where they autonomously perform a subset of the X.25 LAPB/
ISDN LAPD protocol.
Reception of Frames
The logic processing of received S-frames is performed by the HSCX without interrupting the
station (receive ready/not receive ready) and protocol errors (unacceptable N(R) or S-frame
with I field).
I-frames are also processed autonomously and checked for protocol errors. The I-frame will
not be accepted in the case of N(s) error (no interrupt is forwarded to the
immediately confirmed by an S response. If the C sets the HSCX into a "receive not ready"
status, an I-frame will not be accepted (no interrupt) and an RNR response is transmitted.
U-frames are always stored in the RFIFO and forwarded directly to the C. The logic sequence
and the reception of a frame in the auto-mode is illustrated in figure 10.
Note: The state variables N(S), N(R) are evaluated within the window size, i.e. the HSCX
Semiconductor Group
C. The C is merely informed by interrupt with respect to status changes in the opposite
Procedural Support (Layer-2 Functions)
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checks only the Isb of the receive and transmit counter regardless of the selected
modulo count.
updating of transmit and receive counter
evaluation of transmit and receive counter
processing of S commands
flow control with RR/RNR
generation of responses
recognition of protocol errors
transmitting of S commands, if acknowledgement is missing
continuous status query of opposite termination after RNR has been received
programmable timer/repeater functions.
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