AAL2 Implementation
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
44-9
0x20
(cont.)
14
TXM
AAL2 TXB interrupt mask. This bit allows the user to mask the AAL2 TXB interrupt
(AAL2 = 1 and TXB = 1 in the exception queue entry).
0 - AAL2 TXB interrupt is disabled. Exception entry with AAL2 and TXB indication
will not be generated.
1 - AAL2 TXB interrupt is enabled.
Host writes this field. AAL2 does not modify this field.
15
—
Reserved, should be cleared.
0x22
—
TBASE
Transmit BD base. Holds the pointer to the first BD in the AAL0 BD table of this
channel. TBASE represents bits [14–29] of an offset from TBDBASE. Bits [30–31]
are always 00.
This field should be the same value programmed in the TBASE as defined in the
AAL0 TCT of this channel. TBDBASE is defined in the AAL0 parameter RAM of the
SCC that runs this AAL2 channel.
Host writes this field during initialization. AAL2 does not modify this field.
0x24
0-7
—
Reserved, should be cleared.
8–15
TCU
Determines the maximum wait time of CPS-Packets for this channel. The wait time
is defined in units of RISC timer ticks (as defined in RCCR[TIMEP]).
If the user uses the Timer CU mechanism (ET=1), the TCU field should be in the
range of 1-255
Host writes this field during initialization. AAL2 does not modify this field.
0x26
—
AAL2_TACT_PT
R
Active transmit BD pointer. Points to the AAL0 BD currently being processed by
AAL2. The address of the current BD in the table is (AAL2_TACT_PTR * 4) +
TBDBASE. AAL2_TACT_PTR field provides bits [14-29] of the offset; bits [30-31]
are always 00.
Host should write TBASE to this field during initialization. This pointer is advanced
by the AAL2.
0x28
—
AAL2_TQ_BAS
E
Pointer to the first TPD in the AAL2_Tx_Queue. The actual address of the first TPD
is [(AAL2_TQ_BASE * 4) + AAL2_TPD_BASE].
AAL2_TPD_BASE is the base pointer to the TPD space and is defined in the AAL2
parameter area common to all AAL2 channels; see
Section 44.7.1, “AAL2
Parameter RAM.”
The AAL2_TQ_BASE field provides bits [14-29] of the word-aligned offset from
AAL2_TPD_BASE; bits [30-31] are always 00.
Host writes this field during initialization. AAL2 does not modify this field.
0x2A
—
AAL2_TQ_PTR Pointer to the current TPD in the AAL2_Tx_Queue. This is the TPD that the AAL2
functionality is currently processing (or will process next) in AAL2_Tx_Queue.
The address of the current TPD in the AAL2_Tx_Queue is (AAL2_TQ_PTR * 4) +
AAL2_TPD_BASE.
AAL2_TQ_PTR field provides bits [14-29] of the offset; bits [30-31] are always 00.
Host should write AAL2_TQ_BASE to this field during initialization. AAL2 advances
this pointer during normal operation.
0x2C
—
CHEAD
Channel header. This field contains the full (4 bytes) AAL0 buffer header of this
channel. AAL2 appends the CHEAD field to the CPS-PDU to create a complete
AAL0 buffer. The byte ordering of this field is big endian.
Host writes this field during initialization. AAL2 does not modify this field.
0x30–
0x3E
—
—
Reserved, should be cleared.
Table 44-3. AAL2 Transmit Connection Table Field Descriptions (continued)
Offset
Bits
Name
Description
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