Freescale Semiconductor MPC8260 - Manual (Page 918)

Fast Communications Controllers (FCCs)
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
29-20 Freescale Semiconductor
Figure 29-11. Using CD to Control Reception
If it is programmed to envelope data, CD must remain asserted during frame transmission or a CD lost
error occurs. The negation of CD terminates reception. If [CDS] = 0, CD must be sampled by the FCC
before a CD lost is recognized. Otherwise, the negation of CD immediately causes the CD lost condition.
NOTE
If GFMR[CDS] = 1, all CD transitions must occur while the receive clock
is low.
29.12 Disabling the FCCs On-the-Fly
Unused FCCs can be temporarily disabled. In this case, a operation sequence is followed that ensures that
any buffers in use are closed properly and that new data is transferred to or from a new buffer. Such a
sequence is required if the parameters that must be changed are not allowed to be changed dynamically. If
the register or bit description states that dynamic changes are allowed, the following sequences are not
required and the register or bit may be changed immediately. In all other cases, the sequence should be
used.
Modifying parameter RAM does not require the FCC to be fully disabled. See the parameter RAM
description for when values can be changed. To disable all peripheral controllers, set CPCR[RST] to reset
the entire CPM.
1. GFMR[CDS] = 0. CDP=0.
RCLK
First Bit of Frame Data
Notes:
CD Sampled Low
RCLK
CD Sampled High
Last Bit of Frame Data
2. If CD is negated prior to the last bit of the receive frame, CD lost is signaled in the BD.
3. If CDP=1, CD lost cannot occur and CD negation has no effect on reception.
1. GFMR[CDS] = 1. CDP=0.
Notes:
2. If CD is negated prior to the last bit of the receive frame, CD lost is signaled in the BD.
3. If CDP=1, CD lost cannot occur and CD negation has no effect on reception.
Last Bit of Frame Data First Bit of Frame Data
CD Assertion Immediately
Gates Reception CD Negation Immediately
Halts Reception
RXD
(Input)
CD
(Input)
CD
(Input)
RXD
(Input)