MPC8280 datasheet(1282/1386 Pages) FREESCALE

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FCC Transparent Controller

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

38-2

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

38.2

Transparent Channel Operation

The transparent transmitter and receiver operates in the same way as the HDLC controller of the FCC (see

Chapter 37, “FCC HDLC Controller”) except in the following ways:

1. The FPSMR does not affect the transparent controller, only the GFMR does.

2. In Table 37-1 on page 37-3, 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 38.3, “Achieving Synchronization in Transparent Mode.”

38.3

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

38.3.1

In-Line Synchronization Pattern

The transparent channel can be programmed to transmit and receive a synchronization pattern if

GFMR[SYNL]

≠ 0; see Section 30.2, “General FCC Mode Registers (GFMRx).” The pattern is defined in

the FDSR; see Section 30.4, “FCC Data Synchronization Registers (FDSRx).” GFMR[SYNL] defines the

SYNC pattern length. The synchronization pattern is shown in Figure 38-1.

Field

8-Bit Sync Pattern

—

Field

16-Bit Sync Pattern

(Second Byte)

(First Byte)

Figure 38-1. In-Line Synchronization Pattern

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