mt90503 Zarlink Semiconductor, mt90503 Datasheet - Page 68

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

Payload Size
Offset
GFC, VPI,
VCI, OAM,
PTI, CLP
P-Byte
Counter
Field
Table 22 - Description of the Fields for the TX_SAR Control Structure (continued)
Payload Size
Offset
Header
information
P-Byte
Counter
Name of
Field
+4/b15:b10
+4/b9:b3
+8,
+A/b15:b0
+C/b14:b0
Offset /Bits
Address
Used
Byte
Zarlink Semiconductor Inc.
For fully-filled cells, regardless of type, the payload size field is
30h. For partially-filled cells, the payload size indicates the
number of TDM bytes to be placed in each ATM cell. The field
range is from 4h to 2Fh.
Note: 2Fh is an illegal value for partially-filled AAL1cells
For partially-filled AAL5 VTOA, this field must be set to 8h,
10h, 18h, 20h, or 28h.
Offset is used when the VC first starts up, and whenever an
event with the S bit is set in the transmit event scheduler entry.
This shows the delta that must exist between the TX_SAR
read pointer and the TDM write pointer within the circular
buffer. The value for this offset will change depending on the
number of channels in the VC, and on the multiframing
standard used.
Offset’s value is programmed with the maximum number of
bytes of a given channel in an ATM cell, plus three. If an error
is produced when programming Offset, a global tx_slip will be
flagged in the register 0502h, indicating an erroneous
configuration and the possibility of corrupted data.
The Offset between the tx_wrt_pnt (TDM) and the
tx_sar_read_pnt that must be present prior to assembling any
ATM cell whose event in the transmit event scheduler has the
S bit set. This offset is coded as an integer from normal VCs. It
is coded as an multi-frame [1:0] and frame [4:0] number for E1
and T1 VCs.
Header information for the cells to be assembled using this
TX_SAR control structure.
The p-byte counter field is used for the generation of the p-byte
within the cell, or within the multiframe structure.
The p-byte counter is decremented each time a byte of data is
sent, including a CAS byte, but not including an information
byte such as the AAL1 byte or the pointer-byte. Whenever the
counter reaches 0 and must decrement, its value is reset to
p-byte Max field which must be set to 0 by the software.
Whenever a p-byte needs to be generated, the seven LSBs of
the P-byte Counter are the value of the p-byte, with parity
added as the MSB. The decrementing continues until the value
of the P-byte Counter reaches 0 and wraps around again,
ending the multiframe and beginning a new one.
MT90503
68
Description of Field
Data Sheet