mt90528ag2 Zarlink Semiconductor, mt90528ag2 Datasheet - Page 43

• Manufacturer Part Number: mt90528ag2
• Description: 28-port Primary Rate Circuit Emulation Aal1 Sar
• Manufacturer: Zarlink Semiconductor

SDT Mode
Data and CAS, received on the DSTi and CSTi/LOSi pins, respectively, are sampled on edges of either STiCLK[p]
or C4M/C2M. If the TDM port is configured to be in backplane mode, the common clock C4M/C2M is used; if not,
STiCLK[p] is used. Similarly, if the TDM port is in backplane mode, the frame pulse F0 is used to indicate the
beginning of a frame, whereas STiMF[p] is used if the port is configured to be in independent mode.
In ST-BUS applications, a falling edge on STiMF[p]/F0 indicates the beginning of a frame/multiframe pulse. In
Generic applications (and depending on the configuration specified by the user via register bits), either a rising or
falling edge on STiMF[p]/F0 indicates the beginning of a frame/multiframe pulse.
The sampled data and CAS bytes are written to the TDM Input Buffer. In Generic DS1-1.544MHz mode, the framing
bit (aligned with the frame pulse) is discarded by the TDM block, and therefore not transmitted in the ATM cells. The
TDM segmentation process then transfers data and CAS to the SDT Segmentation Circular Buffers, located in
external memory.
SDT Segmentation Circular Buffers
The main function of the SDT Segmentation Circular Buffers is to store data and CAS, coming from the TDM Input
Buffer, for transfer to the TX_SAR. The buffers are composed of 16-bit wide entries, each of which is composed of
the following fields, as shown in Figure 11:
•
•
•
The location of the SDT Segmentation Circular Buffers in external memory is determined by the Segmentation
Circular Buffer Base Address (configured via TDM_SEGMEN_BASE_ADD in the per-port TDM Control Register 2).
The SDT Segmentation Circular Buffer for the first channel of the DS1/E1 stream is located at the word address
specified by TDM_SEGMEN_BASE_ADD. The second is located at TDM_SEGMEN_BASE_ADD + 64 words (128
bytes), etc., as seen in Figure 11. There is one circular buffer for each TDM channel and each buffer is 64 entries
long.
Res (Reserved) - bits<15:12> are unused.
CAS - bits<11:8> are used to store the CAS nibbles.
TDM Data - bits<7:0> store bytes of data received on DSTi.
Port p - Channel 31
Port p - Channel 0
64 words
64 words
Figure 11 - Per-Port SDT Segmentation Circular Buffers
0 0 0 0
0 0 0 0
Res
Res
A B C D
A B C D
Zarlink Semiconductor Inc.
CAS
CAS
MT90528
43
TDM Byte
TDM Byte
Data
Data
Word Address of Start of Buffer =
TDM_SEGMEN_BASE_ADD * 2048d
Byte Address of Start of Buffer =
2 * (TDM_SEGMEN_BASE_ADD* 2048d)
Word Address of Start of Buffer =
TDM_SEGMEN_BASE_ADD * 2048d + 1984d
Byte Address of Start of Buffer =
2 * (TDM_SEGMEN_BASE_ADD * 2048d + 1984d)
Data Sheet