mt90528ag2 Zarlink Semiconductor, mt90528ag2 Datasheet - Page 83

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

002h, regardless of the size of the buffers selected. It must be noted that the Reassembly Circular Buffer Base
Address must correspond to the address given within the TDM SDT Reassembly Control Structure (see Figure 13
on page 46) for the chosen TDM channel destination (port- and channel- specific).
Each 16-bit entry in external memory contains a variety of information. Each entry is composed of the fields shown
in Figure 29 and explained in the text below.
•
•
•
•
•
SDT TDM Data Transfer and CAS Nibble Processing
The overall byte extraction process within the SDT RX_SAR is quite similar to that used by the UDT RX_SAR. In
general, the SDT RX_SAR is responsible for transferring a cell received at the UTOPIA interface to the (one or
many) SDT Reassembly Circular Buffer(s) for the VC. In a cell loss or misinsertion condition, the SDT RX_SAR is
MF - multiframe indicator; this bit is used only when a VC is carrying CAS data (if a VC isn’t carrying CAS,
the MF bits are always zero); the MF bit is set in the buffer for every channel of a VC, each time that the SDT
RX_SAR determines the location of the start of the next multiframe
Res - reserved field; this field always contains a zero
Turn - this field contains a copy of the two most-significant bits of the SDT RX_SAR write pointer for the VC.
These bits represent the “turn” of the circular buffer and are used by the TDM module for underrun detection.
CAS - If CAS data is being processed, this field contains the nibble of data which was last received by this
channel (i.e., in the previous multiframe). CAS data is repeated for an entire multiframe (i.e., 24 consecutive
entries in DS1 case; 16 consecutive entries in E1 case).
TDM Byte - This field contains the TDM data bytes which are extracted from received cells. If dummy cells
have been inserted, this field contains the value of the dummy data programmed by the user.
Table 19 - Formation of SDT Reassembly Circular Buffer Base Addresses to External Memory
Buffer Size
1024 entries
128 entries
256 entries
512 entries
64 entries
MF
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
Figure 29 - Per-Channel SDT Reassembly Circular Buffer
Res
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
{cb_base_add<1:0>,reassembly_circular_buffer_base_add<11:0>,6’b0}
{cb_base_add<0>,reassembly_circular_buffer_base_add<11:0>,7’b0}
{reassembly_circular_buffer_base_add<11:0>,8’b0}
{reassembly_circular_buffer_base_add<10:0>,9’b0}
{reassembly_circular_buffer_base_add<9:0>,10’b0}
Turn
0 1
0 1
0 1
0 1
0 1
0 1
0 1
0 1
0 1
0 1
0 1
0 1
0 1
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
Zarlink Semiconductor Inc.
A B C D
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
CAS
MT90528
Address to External Memory
83
X X X X X X X X
X X X X X X X X
X X X X X X X X
X X X X X X X X
X X X X X X X X
X X X X X X X X
X X X X X X X X
X X X X X X X X
X X X X X X X X
X X X X X X X X
X X X X X X X X
X X X X X X X X
X X X X X X X X
X X X X X X X X
X X X X X X X X
X X X X X X X X
X X X X X X X X
X X X X X X X X
X X X X X X X X
X X X X X X X X
0 0 1 0 1 0 1 0
TDM Byte
Data Sheet