Freescale Semiconductor MPC8260 - Manual (Page 1046)

ATM AAL1 Circuit Emulation Service
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
31-30 Freescale Semiconductor
0x12 0 SPV Structured pointer valid. Should be user-initialized user to zero. Structured format only.
1–3 — Reserved, should be cleared during initialization.
4–15 SP Structured pointer. Used by the CP to calculate the structured pointer. This field should
be initialized by the user to zero. Used in structured format only.
0x14 — RBDCNT RxBD count. Indicates how many bytes remain in the current Rx buffer. Initialized with
MRBLR whenever the CP opens a new buffer.
0x16 0–11 Block Size Used only in structured format. Specifies the structured block size (Block Size = 0xFFF =
4 Kbytes maximum).
Note that when working in CAS mode (CESM=1 and CASM=1), the block size should be
programmed to the superframe block size plus the size of the CAS block. However, when
working in basic mode (CES without CAS: CESM=1 and CASM=0) the block size should
be programmed to the number of MCC slots (Nx64) per frame assigned to this channel.
12 — Reserved, should be cleared during initialization.
13–15 SN Sequence number. Used by the CP to check incoming cell’s sequence number.
0x18 0-7 SCN Super Channel Number.
This field should contain the MCC Super Channel Number that mapped to this ATM
channel. This field must be initialized by the user in CES mode only. See
Section 31.4.7, “Mapping VC Signaling to CAS Blocks .”
8 RXBM Receive buffer interrupt mask
0 The receive buffer event of this channel is disabled. (The event is not sent to the
interrupt queue.)
1 The receive buffer event of this channel is enabled.
9 SLIPIM Slip interrupt mask
0 The slip interrupts SLIPS and SLIPE are both masked.
1 When the receiver switches to hunt mode due to a 3-step-SN algorithm fault, or due to
two successive mismatched pointers, or due to a pre-overrun condition, the SLIPS
interrupt is sent to the interrupt queue. See
Section 31.6, “3-Step-SN Algorithm ,” and
Section 31.13, “AAL1 CES Exceptions .” When the receiver resynchronizes, SLIPE
interrupt is sent to the interrupt queue. Note that this is the error reporting mechanism
during automatic data forwarding (ATM-to-TDM bridging).
10-11 — Reserved, should be cleared during initialization.
12-15 CASBS CAS block size.This field contains the number divided by two (N/2) of signaling nibbles
mapped to this ATM channel. See Section 31.4.7, “Mapping VC Signaling to CAS
Blocks .”
Note that if the number of signaling nibbles is odd, this field should be programmed to
(N+1)/2. See Section 31.2.2, “Signaling Path .”
Example: ESF with three T1 time slots connected to one ATM channel. The Data_Size
= 3*24 = 72 octets and the CAS Block= 2 octets (N=3, (N+1)/2 = 2), so in this case the
Block_Size = 72+2 = 74
Table 31-6. AAL1 CES Protocol-Specific RCT Field Descriptions (continued)
Offset Bits Name Description