mt90503 Zarlink Semiconductor, mt90503 Datasheet - Page 49

• Manufacturer Part Number: mt90503
• Description: 2048vc Aal1 Sar
• Manufacturer: Zarlink Semiconductor

The CAS bits are always kept in the highest four bits of the last byte.
In addition to storing the data in the circular buffers, the parity bits of the data memory are used to detect underruns
generated on the ATM link. When the RX_SAR writes data to the circular buffers, it writes a ‘1’ in the parity bit of the
memory’s low byte. When the TX_SAR writes data bytes in the buffer, it writes a ‘0’ to the parity bit of the memory’s
low byte. Therefore, when the TDM reads the data from the circular buffer, it expects to read a ‘1’ from the parity bit.
+1A
+1C
+1E
+2A
+2C
+2E
+3A
+3C
+3E
+10
+12
+14
+16
+18
+20
+22
+24
+26
+28
+30
+32
+34
+36
+38
+A
+C
+E
+0
+2
+4
+6
+8
Figure 16 - TDM Circular Buffer (one MultiFrame in T1 mode)
EP
b15
b14
TX CAS
b13
Reserved
High byte
TX Byte 10
TX Byte 11
TX Byte 12
TX Byte 13
TX Byte 14
TX Byte 15
TX Byte 16
TX Byte 17
TX Byte 18
TX Byte 19
TX Byte 20
TX Byte 21
TX Byte 22
TX Byte 23
TX Byte 0
TX Byte 1
TX Byte 2
TX Byte 3
TX Byte 4
TX Byte 5
TX Byte 6
TX Byte 7
TX Byte 8
TX Byte 9
b12
b11
Zarlink Semiconductor Inc.
b10
MT90503
b9
b8
Underrun Detection Bits
49
OP
b7
RX CAS
b6
Low byte
b5
RX Byte 10
RX Byte 11
RX Byte 12
RX Byte 13
RX Byte 14
RX Byte 15
RX Byte 16
RX Byte 17
RX Byte 18
RX Byte 19
RX Byte 20
RX Byte 21
RX Byte 22
RX Byte 23
RX Byte 0
RX Byte 1
RX Byte 2
RX Byte 3
RX Byte 4
RX Byte 5
RX Byte 6
RX Byte 7
RX Byte 8
RX Byte 9
b4
b3
b2
b1
b0
Data Sheet