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DPR_base
Channel 0 Parameter
Channel 1 Parameter
Channel j Extra
Parameter
Global MCC
MCCBASE
Parameters
27.3 Global MCC Parameters
The global MCC parameters are described in Table 27-1.
Table 27-1. Global Multiple-Channel Parameters
1
Offset
Name
Width
0x00
MCCBASE
Word
0x04
MCCSTATE Hword Multi-channel controller state, used by the CP for global state deÞnition (reserved for
0x06
MRBLR
Hword Maximum receive buffer length (user-initialized). DeÞnes the maximum number of
0x08
GRFTHR
Hword Global receive frame threshold. Used to reduce interrupt overhead that can occur
0x0A
GRFCNT
Hword Global receive frame count. A decrementor counter used to implement the GRFTHR
MOTOROLA
Buffer Descriptor
Table Base Address
DPR
x8
RBASE
TBASE
x8
Figure 27-1. BD Structure for One MCC
Multi-channel controller base pointer. User-initialized parameter points to the starting
address of a 512-Kbyte BD segment in external memory.
the user)
bytes written to a receive buffer before moving to the next buffer for this channel.
This value must be a multiple of 8.
when many short HDLC frames arrive that each cause an RXF interrupt. Setting all
bits enables every interrupt event. Setting a GRFTHR value can limit the frequency
of RXF interrupts. Note that an RXF event is written to the interrupt queue on each
received frame but GINT is set only when the number of RXF events (by all
channels) reaches the GRFTHR value. This parameter does not need to be reset
after an interrupt.
feature. It should be initialized to the GRFTHR value. Setting all bits enables every
interrupt event. The CP writes an entry in a circular interrupt table and decrements
GRFCNT each time a frame is received. When GRFCNT underßows the CP
generates an interrupt and copy GRFTHR to GRFCNT. This parameter does not
need to be reset after an interrupt.
Chapter 27. Multi-Channel Controllers (MCCs)
Part IV. Communications Processor Module
External Memory
+
Channel j RxBD
+
Channel j TxBD
Description
512 Kbytes
Table
Table
27-3
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