Motorola PowerQUICC II MPC8280 Series Reference Manual page 1011

RCLK
RXD
(Input)
CD
(Input)
Notes:
1. GFMR[CDS] = 0. CDP=0.
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.
RCLK
RXD
(Input)
CD
(Input)
Notes:
1. GFMR[CDS] = 1. CDP=0.
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.
Figure 30-12. 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.
If GFMR[CDS] = 1, all CD transitions must occur while the
receive clock is low.
30.12 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.
MOTOROLA Chapter 30. Fast Communications Controllers (FCCs)
Freescale Semiconductor, Inc.
First Bit of Frame Data
CD Sampled Low
First Bit of Frame Data
CD Assertion Immediately
Gates Reception
NOTE
For More Information On This Product,
Go to: www.freescale.com
Disabling the FCCs On-the-Fly
Last Bit of Frame Data
CD Sampled High
Last Bit of Frame Data
CD Negation Immediately
Halts Reception
30-21