
DATA SHEET
PM7367 FREEDM-32P32
ISSUE 2
PMC-1991499
FRAME ENGINE AND DATA LINK MANAGER
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMER’S INTERNAL USE
233
framing byte. Thus, on the first rising edge of TCLK[0] after the extended
quiescent period, a downstream block can sample the m.s.b. of time-slot 1.
When CEN is set low, link #0 is unchannelised and the E1 register bit is
ignored. TCLK[0] is gapped during non-data bytes. The choice between
treating all data bits as a contiguous stream with arbitrary byte alignment or
byte aligned to gaps in TCLK[0] is controlled by the BSYNC bit.
E1:
The E1 frame structure select bit (E1) configures link #0 for channelised E1
operation when CEN is set high. TCLK[0] is held quiescent during the FAS
and NFAS framing bytes. The most significant bit of time-slot 1 is placed on
TD[0] on the last falling edge of TCLK[0] ahead of the extended quiescent
period. Link data is present at time-slots 1 to 31. When E1 is set low and
CEN is set high, link #0 is configured for channelised T1 operation. TCLK[0]
is held quiescent during the framing bit. The m.s.b. of time-slot 1 is placed on
TD[0] on the last falling edge of TCLK[0] ahead of the extended quiescent
period. Link data is present at time-slots 1 to 24. E1 is ignored when CEN is
set low.
BSYNC:
The byte synchronisation enable bit (BSYNC) controls the interpretation of
gaps in TCLK[0] when link #0 is in unchannelised mode (CEN set low).
When BSYNC is set high, the data bit on TD[0] clocked in by a downstream
device on the first rising edge of TCLK[0] after an extended quiescent period
is considered to be the most significant bit of a data byte. When BSYNC is
set quiescent , gaps in TCLK[0] carry no special significance. BSYNC is
ignored when CEN is set high.