MT92220 Datasheet, PDF (129/210 Pages) Zarlink Semiconductor Inc – 1023 Channel Voice Over IP/AAL2 Processor

Data Sheet
The format of the RX RTP CPU Channel Structure is the following:
MT92220
b 15 b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
+0 _{A B 1 1 1}
1
RX CPU Buffer Index [8:0]
+2
0x0000
+4
HFE
0x00
+6
Discharge Rate [5:0]
0000
+8
Maximum Bucket Fill [15:0]
+A
Last Packet Local Time Stamp [23:8]
+C Last Packet Local Time Stamp [7:0] _I
Current Bucket Fill [21:16]
+E
Current Bucket Fill [15:0]
+10
Received Packet Count [15:0]
+12
Received Octet Count [31:16]
+14
Received Octet Count [15:0]
Figure 70 - RX RTP CPU Channel Structure
Field
A
B
RX CPU Buffer Index
HFE
Discharge Rate
Maximum Bucket Fill
CBF
Description
Clock Recovery channel A. When this field is set, an Adaptive Clock Recovery RTP
Event Structure using this packet’s sequence number and time stamp fields will be
written to the Adaptive clock recovery queue A.
Clock Recovery channel B. When this field is set, an Adaptive Clock Recovery RTP
Event Structure using this packet’s sequence number and time stamp fields will be
written to the Adaptive clock recovery queue B.
Index in the RX CPU Buffer Control Table in SSRAM B.
Half Full Interrupt Enable. When ‘1’, if the RX CPU Buffer for this channel is more
than half full, the interrupt_error_alarm will be forced active. This alarm should force
the software to empty out packets in all RX CPU buffers.
Long term rate at which bytes can be received on this RX CPU channel. The current
bucket fill is reduced at this rate. The rate is defined as a number of bytes per frame
that can be sent into the RX CPU buffer. This is a floating point number; it has two
bits of mantissa (excluding the hidden leading ‘1’) and 4 bits of exponent. Zero is not
a legal value. The minimum rate is 4 kbps, which is defined as mantissa = “100” and
exponent = “0001”. So to calculate the rate, the following equation can be used: 4
kbps * (mantissa/8) * (2^exponent).
Up to this many bytes can be contained in the “policing bucket” of this RX CPU
channel before packet discarding takes place. Largest value is 0x0000 (which
means 65536 bytes), smallest value is 0x1 (which means 1 byte).
Current Bucket Fill. Current fill of the “policing bucket” in 1/64th of a byte. This field
should be initialized to all zeros by software.
Table 54 - Fields and Description
Zarlink Semiconductor Inc.
129