Motorola MPC8260 - Manual (Page 735)

MOTOROLA Chapter 27. Multi-Channel Controllers (MCCs) 27-5
Part IV. Communications Processor Module
27.4 Channel Extra Parameters
Table 27-2 describes extra parameters. This table is indexed by logical channel number.
27.5 Super-Channel Table
The super channel t able entry redirects an MCC slot to a different channel number. For this
reason, the transmitter super channel uses more FIFO (2 bytesÑhalf of a single channel
transmitter FIFOÑmultiplied by the number of the channels in the super channel) in the
MCC hardware.
On the transmitter side, super channels must be deÞned in the SI RAM (see Section 14.4.3,
ÒProgramming SIx RAM Entries,Ó for details) and a super-channel table must be created.
On the receiver side, the transparent super channels that require slot synchronization must
be programmed in the SI RAM as super channels (the slot synchronization ensures that the
data is aligned in the receiver buffer starting from the Þrst time slot after a sync pulse). In
this case, 1 byte of FIFO is allocated for each super channel. Transparent super channels
that do not require slot synchronization and HDLC super channels can be programmed in
the SI RAM as regular channels pointing to the same MCC channel. In this case the FIFO
allocated for each super channel is 2 bytes (and the CP load will be lower).
The example in Figure 27-3 shows the SI RAM programming and the super-channel table
for two transmitter super channels, one including slots 1, 6, and 7 and the second 2, 3, and
4. Figure 27-4 shows the SI RAM programming for the same transparent receiver super
Table 27-2. Channel Extra Parameters
Offset 1
1 The offset relative to dual-port RAM base address + XTRABASE + 8*CH_NUM
Name Width Description
0x00 TBASE Hword TxBD base address. Offset of the channelÕs TxBD table relative to the MCCBASE (The
base address of the BD table for this channel MCCBASE+8*TBASE)
0x02 TBPTR Hword TxBD pointer. Offset of the current BD relative to the MCCBASE. TBPTR is user-initialized
to TBASE before enabling the channel or after a fatal error before reinitializing the
channel. (The address of the BD in use for this channel MCCBASE+8*TBPTR)
0x04 RBASE Hword RxBD base address. Offset of the channelÕs RxBD table relative to the MCCBASE. (The
base address of the BD table for this channel MCCBASE+8*RBASE)
0x06 RBPTR Hword RxBD pointer. Offset of the current BD relative to the MCCBASE. RBPTR is user-
initialized to RBASE before enabling the channel or after a fatal error before reinitializing
the channel. (The address of the BD in use for this channel MCCBASE+8*RTBPTR)
Bits 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Field 0 0 Channel Number 0 0 0 0 0 0
Address DPR_base_address+SCTPBASE+2*Virtual_Channel_Number
(Virtual_channel_number is the number written in the MCSEL Þeld of the corresponding SI RAM entry)
Figure 27-2. Super Channel Table Entry