MT90500 Mitel Semiconductor, MT90500 Datasheet - Page 53

• Manufacturer Part Number: MT90500
• Description: Multi-Channel ATM AAL1 SAR
• Manufacturer: Mitel Semiconductor

PSEL bits are one-hot bits which represent cells with sequence numbers 0, 2, 4, and 6, respectively - see
Table 10 below for an explanation of bit operation). The MT90500 also supports proprietary pointer
transmissions in which a P-byte is sent every 4 cells (PSEL = A hex) or every other cell (PSEL = F hex). Using
these proprietary methods, up to 122 channels can be sent on a particular VC, but this is only possible if the
receiving chip can handle the extra P-bytes during a cycle.
Each “TX Circular Buffer Address” appended to the end of the structure points to a 64-byte circular buffer in
external memory.
0000
1000
1010
1111
Figure 18 - a: Sample Three-Channel Transmit Control Structure (AAL1/CBR-AAL0)
Figure 18 - b: Sample One-Channel Transmit Control Structure (CBR-AAL5)
2018C
2018A
2018E
20190
20184
20186
20188
2018C
20180
20182
2018E
20190
2018A
20184
20186
20188
20180
20182
Sequence # 0
Pointer sent.
Pointer sent
Pointer sent
V
V
V
VPI(11:8)
V
15
VPI(11:8)
15
GFC /
GFC /
Current Entry
Current Entry
First Entry
First Entry
HEC
Table 10 - Effect of PSEL Field on P-byte Generation
Offset
HEC
Offset
TX Circular Buffer Address
TX Circular Buffer Address
TX Circular Buffer Address
0000 0000 0000 0000
0000 0000 0000 0000
TX Circular Buffer Address
VCI(11:0)
VCI(11:0)
VPI(7:0)
VPI(7:0)
Sequence # 2
SEQ
A
Pointer sent
A
SEQ
8
8
R S 00
AS
R S 00
AS
7
7
No pointers are sent.
-
-
Last Entry
Last Entry
Payload Size
Circ. Buf. Pnt.
Payload Size
Circ. Buf. Pnt.
VCI(15:12)
VCI(15:12)
PTI
PSEL
PTI
PSEL
Sequence # 4
C1
C1
0
Pointer sent
Pointer sent
0
0
0
-
First Entry location = 2018C
First Entry location = 20190
Last Entry location = 20190
Last Entry location = 20190
Sequence #6
Pointer sent
-
-
Last Entry field
First Entry field
Last Entry field
First Entry field
1 0 0 1 0 0 0
1 0 0 0 1 1 0
1 0 0 1 0 0 0
1 0 0 1 0 0 0
ANSI and ITU-T - AAL0, AAL5,
ANSI and ITU-T - AAL1-SDT
pointerless AAL1 Structured
Data Transfer, and partially-
A
A
0
0
Applicable Standards
A
A
0
0
ANSI - AAL1- SDT
ANSI - AAL1-SDT
filled cells
MT90500
53