FCC Transparent Controller
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
37-2
Freescale Semiconductor
•
Reverse data mode
•
Another protocol can be performed on the FCC’s other half (transmitter or receiver) during
transparent mode
•
External BD table
37.2
Transparent Channel Operation
The transparent transmitter and receiver operates in the same way as the HDLC controller of the FCC (see
Chapter 36, “FCC HDLC Controller”
) except in the following ways:
1. The FPSMR does not affect the transparent controller, only the GFMR does.
2. In Table 36-1 on page 36-3, MFLR, HMASK, RFTHR, and RFCNT must be cleared for proper
operation of the transparent receiver.
3. Transmitter synchronization has to be achieved using CTS before the transmitter begins sending;
see
Section 37.3, “Achieving Synchronization in Transparent Mode.”
37.3
Achieving Synchronization in Transparent Mode
Once the FCC transmitter is enabled for transparent operation in the GFMR, the TxBD is prepared for the
FCC, and the transmit FIFO is preloaded by the SDMA channel, transmit synchronization must be
established before data can be sent.
Similarly, once the FCC receiver is enabled for transparent operation in the GFMR and the RxBD is made
empty for the FCC, receive synchronization must occur before data can be received. The synchronization
process gives the user bit-level control of when the transmission and reception begins. The methods for
this are as follows:
•
An in-line synchronization pattern
•
External synchronization signals
•
Automatic sync
37.3.1
In-Line Synchronization Pattern
The transparent channel can be programmed to transmit and receive a synchronization pattern if
GFMR[SYNL]
≠
0; see
Section 29.2, “General FCC Mode Registers (GFMRx).”
The pattern is defined in
the FDSR; see
Section 29.4, “FCC Data Synchronization Registers (FDSRx).”
GFMR[SYNL] defines the
SYNC pattern length. The synchronization pattern is shown in
Figure 37-1
.
The receiver synchronizes on the synchronization pattern located in the FDSR. For instance, if an 8-bit
SYNC is selected, reception begins as soon as these eight bits are received, beginning with the first bit
0
7
8
15
Field
8-Bit Sync Pattern
—
Field
16-Bit Sync Pattern
(Second Byte)
(First Byte)
Figure 37-1. In-Line Synchronization Pattern
Summary of Contents for MPC8250
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