Super Channel Initialization; Mcc Latency And Performance - Motorola MPC8260 PowerQUICC II User Manual

Part IV. Communications Processor Module

27.12.2 Super Channel Initialization

The following steps initialize and start a super channel (after reset of after a fatal error):
1. Program the SI as required for a super channel but do not enable the TDM.
2. Issue a STOP command as described in Section 27.9, ÒMCC Commands.Ó
3. Enable the TDM.
4. Initialize the MCC parameters (in DPR and external memory).
5. Enable the MCC channel(s) as described in Section 27.6.1, ÒInternal Transmitter
State (TSTATE),Ó and Section 27.6.4, ÒInternal Receiver State (RSTATE).Ó
The following sequence must be followed to stop a super channel in order to change the SI:
1. Issue a STOP command for the respective channel as described in Section 27.9,
ÒMCC Commands.Ó
2. Disable the TDM.
3. Change the SI.
4. Enable the TDM.
5. If necessary, change the MCC parameters (in DPR and external memory).
6. Enable the MCC channel(s) as described in Section 27.6.1, ÒInternal Transmitter
State (TSTATE),Ó and Section 27.6.4, ÒInternal Receiver State (RSTATE).Ó
Under the following restrictions, the SI can be changed using the SI shadow while the
channel is active:
¥ Both the primary and the shadow conÞguration of the SI RAM must observe the
conÞguration of the super channel. Note that the super-channel table and MCCF
register cannot be changed dynamically.
¥ It is not possible to add dynamically to a super channel a time slot previously used
by a single-channel and had a width different from 8 bits.
¥ A time slot that was previously used by a single channel and had a width different
from 8 bits cannot be added dynamically to a super channel.

27.13 MCC Latency and Performance

The MCC transfers data to/from the memory 8 bytes at a time. Considering this and the
internal receiver FIFO (of 2 bytes/channel), the receiver latency (time since data on a
channel is serialized until the respective data is written to memory) can be from 8Ð10 frame
periods.
If no super channels are active, the MCC can handle aggregate data rates of up to 16 Mbps
on each of the four channel subgroups. If super channels are used this performance is
limited to 8 Mbps.
27-26 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA