Motorola MPC8260 - Manual (Page 835)

29-55 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA
Part IV. Communications Processor Module
Table 29-23 describes AAL1 protocol-speciÞc TCT Þelds.
29.10.2.3.3 AAL0 Protocol-SpeciÞc TCT
Figure 29-33 shows the AAL0 protocol-speciÞc TCT.
Table 29-23. AAL1-Specific TCT Field Descriptions
Offset Bits Name Description
0x10 0-1 Ñ Reserved, should be cleared.
2Ð7 VOS Valid octet size. Partially Þlled cell mode only. SpeciÞes the number of valid octets
from the beginning of the AAL1 user data Þeld. For unstructured service, values 1-47
are valid; for structured service, values 1-46 are valid.
8 PFM Partially Þlled mode.
0 Partially Þlled cells mode is not used.
1 Partially Þlled cells mode is used. The transmitter copies only valid octets from the
buffer to the AAL1 cell. The size of the valid octets from the beginning of the AAL1
user data Þeld is speciÞed in the VOS (valid octet size) Þeld.
9 SRT Synchronous residual time stamp. Unstructured format only. The MPC8260 supports
SRTS generation using external logic. If this mode is enabled, the MPC8260 reads the
SRTS from external logic and inserts it into four cells for which SN = 1, 3, 5, or 7. The
MPC8260 reads the new SRTS from external logic every eight cells. (See
Section 29.15, ÒSRTS Generation and Clock Recovery Using External Logic.Ó)
0 SRTS mode is not used.
1 SRTS mode is used.
10 SPF Structured pointer ßag. Indicates that a structured pointer has been inserted in the
current block. The user should initialize this Þeld to zero. Used by the CP only.
11 STF Structured format
0 Unstructured format is used.
1 Structured format is used.
12 Ñ Reserved, should be cleared.
13Ð15 SN Sequence number Þeld. Used by the CP to check the incoming cells SN. Initialize to 0.
0x12 0Ð3 SRTS
Device
Used to select a SRTS device. The SRTS device address is SRTS_BASE[0Ð
27]+SRTS_DEVICE[28:31]. SRTS_BASE is taken from the parameter RAM and is 16-
byte aligned.
4Ð15 Block Size Used only in structured format. SpeciÞes the structured block size (Block Size
= 0xFFF = 4 Kbytes maximum).
0x14 0Ð3 SRTS_TMP Before a cell with SN = 1 is sent, the CP reads the SRTS code from external SRTS
logic, writes it to SRTS_TMP, and then inserts SRTS_TMP into the next four cells with
an odd SN.
4Ð15 SP Structured pointer. Used by the CP to calculate the structured pointer. Initialize to 0.
Structured format only.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Offset + 0x10 Ñ 0 CR10 Ñ ACHC Ñ
Offset + 0x12 Ñ
Offset + 0x14
Figure 29-33. AAL0 Protocol-Specific TCT