SAB82538 Datasheet, PDF (67/253 Pages) Infineon Technologies AG – ICs for Communications

SAB 82538
SAF 82538
q After reception of an EOP sequence a Secondary can go to the ON Loop state. As
opposed to the Off Loop State, all data is forwarded to the next station with one bit
delay.
q If a Secondary is requested (polled) by the Primary to transmit data or responses, it
has to wait for reception of a further EOP sequence. By flipping the seventh “1” of the
EOP sequence to “0” it generates a flag sequence and consequently all following
Secondary Stations are inhibited from sending. Simultaneously, RxD is disconnected
from TxD and transmission of a frame (or several frames) may start (Active ON Loop
state). After terminating transmission the station reconnects RxD to TxD. Thus, an
EOP sequence is formed and another station may start data transmission.
Processing the EOP sequences is handled automatically by the ESCC8: commands
(GLP, GALP in register CCR1) and state indications (interrupts EOP, OLP, AOLP in
register ISR1) are provided to control and monitor the state of the ESCC8 as Secondary
Station.
Figure 32 shows the state diagram for the Secondary. Note that in order to be able to
hold “Active On Loop” state “flags” has to be selected as interframe time fill, as opposed
to “idle”.
Note: The Primary Station has to operate in standard SDLC mode.
Figure 32
State Diagram of SDLC Loop/Secondary
Reception of Frames
SDLC Loop as special variant of the SDLC protocol works in half-duplex normal
response mode, that means that data transmission and data reception at the same time
is not permitted. Normally, data reception is only possible in the On Loop state.
The ESCC8, however, allows data reception in every state. Activation/deactivation of the
receiver is effected by the user by programming the RAC bit in register MODE.
Semiconductor Group
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