CX28394/28395/28398
3.0 Registers
Quad/x16/Octal—T1/E1/J1 Framers
3.15 Data Link Registers
0B2—RDL #2 FIFO Fill Control (RDL2_FFC)
7
6
5
4
3
2
1
0
MSG_FILL[1]
MSG_FILL[0]
FFC[5]
FFC[4]
FFC[3]
FFC[2]
FFC[1]
FFC[0]
MSG_FILL[1:0]
Unformatted Message Fill Limit—This is applicable only for Pack8 and Pack6 modes. The
message fill limit selects how many receive FIFO locations [RDL2; addr 0B3] are filled before
the receive data link generates an RFULL interrupt [ISR1; addr 00A] and a corresponding
RDL2 Partial message status word entry. Fill limit thus determines how many bytes constitute
an unformatted message. The fill limits give the processor an alternative to using RNEAR
interrupts to signal the end of a received unformatted message. The number of bits per
unformatted message must divide evenly by the number of bits monitored per multiframe. For
example, SLC applications monitor Fs bits during even frames for a total of 36 bits monitored
out of 72 frames. Using Pack6 mode, the group of 36 Fs bits from each SLC multiframe can be
chosen to constitute one unformatted message. This is accomplished by selecting a message
fill limit which equals 6 bytes (of 6 bits/byte). In the SLC example, an RFULL interrupt would
then be generated every 9 ms on each SLC multiframe boundary. Fill limits provided for T1
cases are multiples of 6 bytes (i.e. 6, 12 or 18 FIFO locations) to hold one or more multiframes
worth of monitored data. In E1 mode, fill limits are multiples of 8 bytes to correspond with the
16-frame multiframe lengths (i.e. monitoring CRC4 in MFAS framing mode or TS16 in CAS
framing mode).
T1/E1N
MSG_FILL[1:0]
Message Fill Limit
Disabled
8 bytes
X
0
0
0
1
1
1
00
01
10
11
01
10
11
16 bytes
24 bytes
6 bytes
12 bytes
18 bytes
FFC[5:0]
Near Full FIFO Threshold—Selects FIFO depth of near full interrupt [RNEAR; addr 00A] and
near full level status [RNEAR2; addr 0B4]. The RNEAR interrupt and RNEAR2 indicator are
both activated when the number of empty FIFO locations equals the selected threshold. The
threshold controls how many data and/or status bytes (64 minus threshold value) the processor
must read from RDL2 after RNEAR interrupt to clear the RNEAR2 indicator as well as how
much time remains (in bytes) for the processor to read RDL2 before receive FIFO is full. If a
receive message is in progress when the near full threshold is reached, the receiver issues a
message interrupt [RMSG; addr 00A] and places a Partial message in the receive FIFO.
FFC[5:0]
00 0000
00 0001
00 0010
|
Empty @ RNEAR
None
Filled @ RNEAR
64 = RFULL
63 filled
1 empty FIFO location
2 empty FIFO locations
|
62 filled
|
11 1110
11 1111
62 empty FIFO locations
63 empty FIFO locations
1 filled
0 filled = empty
100054E
Conexant
3-87
CONEXANT [ CONEXANT SYSTEMS, INC ]
