AAL2 Implementation
MPC885 PowerQUICC Family Reference Manual, Rev. 2
44-6
Freescale Semiconductor
Table 44-2
describes the TPD fields.
0
1
2
3
4
6
7
8
15
0
R
—
W
INT
—
CM
—
2
—
4
TP_PTR
6
Figure 44-1. Transmit Packet Descriptor (TPD)
Table 44-2. TPD Field Descriptions
Offset
Bits
Name
Description
0x00
0
R
Ready. Determines whether the CPS-Packet is ready for transmission.
0 The CPS-Packet associated with this TPD is not ready for transmission. Host is free to
manipulate the TPD or its associated CPS-Packet.
1 The CPS-Packet associated with this TPD has not been packed or is currently being
packed into the active AAL0 buffer. Host may not write into this TPD or its associated
CPS-Packet once this bit is set.
Host sets this bit after the CPS-Packet associated with this TPD is ready for transmission.
AAL2 clears this bit after the CPS-Packet has been packed into the active AAL0 buffer.
During initialization, the host should clear the ready bit in all TPDs.
0x00
1
—
Reserved, should be cleared.
0x00
2
W
Wrap. Determines whether this is the last TPD in the AAL2_Tx_Queue.
0 This is not the last TPD in the AAL2_Tx_Queue.
1 This is the last TPD in the AAL2_Tx_Queue. After the CPS-Packet associated with this
TPD is packed into the active AAL0 buffer, AAL2 returns to the beginning of the queue
(using the TPD pointed to by AAL2_TQ_BASE). The number of TPDs in the queue is
programmable and is determined only by the W bit.
Host writes this field during initialization. AAL2 does not modify this field.
0x00
3
INT
Determines whether interrupt is generated after this CPS-Packet is packed into the AAL0
buffer.
0 No interrupt is generated after this CPS-Packet has been packed
1 After the CPS-Packet is packed (and if AAL2_TCT[TPI] is set), AAL2 adds an entry to
the exception queue with the AAL2 bit and TXB bit set. The global interrupt count
(INT_CNT) is decremented. If the counter reaches zero, SCCE[GINT] or IDSR1[GINT]
is set, and an interrupt is generated to the host.
Host writes this field during initialization. AAL2 does not modify this field.
0x00
4–6
—
Reserved, should be cleared.
0x00
7
CM
Continuous mode. Determines whether the CPS-Packet associated with this TPD is
marked as available to the host (R = 0) after processing by the CP.
0 Normal operation.
1 The R bit is not cleared after the TPD is closed, allowing the associated CPS-Packet to
be automatically retransmitted the next time the CP accesses this TPD.
Host writes this field during initialization. AAL2 does not modify this field.
0x00
8–15
—
Reserved, should be cleared.
Summary of Contents for PowerQUICC MPC870
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