MT92220BG Zarlink Semiconductor, MT92220BG Datasheet - Page 26

• Manufacturer Part Number: MT92220BG
• Description: Description = 1023 Channel Voice Over IP/AAL2 Processor ;; Package Type = Epbga ;; No. Of Pins = 608
• Manufacturer: Zarlink Semiconductor

26
The module uses an external 32-bit SDRAM to buffer all the packets in transit and applies a linked list technique to
allocate the blocks of memory in the SDRAM. Each packet, as it enters the module, is broken down into 48-byte
payload blocks. These blocks are stored one at a time in SDRAM. A 19-bit link pointer links together the blocks that
make up the packet. A link value of 00000h indicates that this block is the last one in the packet. Each block
occupies 64 bytes of SDRAM. The following figure 4 illustrates the format of blocks as they are kept in external
SDRAM.
+1C
+2C
+3C
+10
+14
+18
+20
+24
+28
+30
+34
+38
+C
+0
+4
+8
b31
b30
b29
b28
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
b27
b26
b25
b24
Figure 4 - Packet Block Memory and Format
b23
b22
Multicast Sum
+100
+140
+180
+C0
+40
+80
b21
+0
Figure 5 - Packet Block Format
b20
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Packet Block Memory
Zarlink Semiconductor Inc.
b19
b18
b17
b16
b15
b14
b13
b12
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Forward Link Handle [24:6]
b11
b10
b9
b8
b7
b6
b5
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
Payload
b4
b3
b2
b1
b0