
PEB 20542
PEF 20542
Functional Overview
Data Sheet
57
2000-09-14
3.2.3.6
Clock Mode 5a (Time Slot Mode)
This operation mode has been designed for application in time-slot oriented PCM
systems.
Note: For correct operation NRZ data coding/encoding should be used.
The receive and transmit clock are common for each channel and must be supplied
externally via pin RxCLK. The SCC receives and transmits only during fixed time-slots.
Either one time-slot
–
of programmable width (1
…
512 bit, via TTSA and RTSA registers), and
–
of programmable location with respect to the frame synchronization signal (via pin
FSC)
or up to 32 time-slots
–
of constant width (8 bits), and
–
of programmable location with respect to the frame synchronization signal (via pin
FSC)
can be selected.
The time-slot locations can be programmed independently for receive and transmit
direction via TTSA/RTSA and PCMTX/PCMRX registers.
Depending on the value programmed via those registers, the receive/transmit time-slot
starts with a delay of 1 (minimum delay) up to 1024 clock periods following the frame
synchronization signal.
Figure 18
shows how to select a time-slot of programmable width and location and
Figure 19
shows how to select one or more time-slots of 8-bit width.
If bit
’
TOE
’
in register
CCR0L
is set, the selected transmit time-slot(s) is(are) indicated at
an output status signal via pin TxCLK, which is driven to
‘
low
’
during the active transmit
window.
Bit
’
TSCM
’
in register
CCR1H
determines whether the internal offset counters are
continuously running even if no synchronization pulse is detected at FSC signal or
stopping at their maximum value.
In the continuous case the repetition rate of offset counter operation is 1024 transmit or
receive clocks respectively. An FSC pulse detected earlier resets the counters and starts
operation again.
In the non-continuous case the time slot assigner offset counter is stopped after the
counter reached its maximum value and is started again if an FSC pulse is detected.