PM7384 FREEDM-84P672
DATA SHEET
PMC-1990445
ISSUE 5
FRAME ENGINE AND DATA LINK MANAGER 84P672
SBI
SBI
RCAS
SBI
SBI
RCAS
Link
No.
SBI
SBI
RCAS
Link
No.
SPE Trib.
Link
No.
SPE Trib.
SPE Trib.
No.
1
No.
23
No.
2
No.
23
No.
3
No.
23
66
69
72
75
78
81
67
70
73
76
79
82
68
71
74
77
80
83
1
1
1
1
1
24
25
26
27
28
2
2
2
2
2
24
25
26
27
28
3
3
3
3
3
24
25
26
27
28
Links containing a T1/J1 or an E1 stream may be channelised. Data at each
time-slot may be independently assigned to a different channel. The RCAS672
performs a table lookup to associate the link and time-slot identity with a
channel. The position of T1/J1 and E1 framing bits/bytes is identified by frame
pulse signals generated by the SBI PISO blocks. Links containing a DS-3
stream are unchannelised, i.e. all data on the link belongs to one channel. The
RCAS672 performs a table lookup using only the link number to determine the
associated channel, as time-slots are non-existent in unchannelised links. Links
may additionally be configured to operate in an unframed “clear channel” mode,
in which all bit positions, including those normally reserved for framing
information, are assumed to be carrying HDLC data. Links so configured
operate as unchannelised regardless of link rate and the RCAS672 performs a
table lookup using only the link number to determine the associated channel.
9.4.1 Line Interface
There are 84 line interface blocks in the RCAS672. Each line interface block
contains a bit counter, an 8-bit shift register and a holding register that, together,
perform serial to parallel conversion. Whenever the holding register is updated,
a request for service is sent to the priority encoder block. When acknowledged
by the priority encoder, the line interface responds with the data residing in the
holding register.
To support channelised links, each line interface block contains a time-slot
counter. The time-slot counter is incremented each time the holding register is
updated and is reset on detection of a frame pulse from the SBI PISO blocks.
For unchannelised or unframed links, the time-slot counter is held reset.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
37
PMC [ PMC-SIERRA, INC ]
