MPC8280 datasheet(760/1386 Pages) FREESCALE

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SCC BISYNC Mode

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

23-6

Freescale Semiconductor

The control character table lets the BISYNC controller recognize the end of the current block. Because the

controller imposes no restrictions on the format of BISYNC blocks, software must respond to received

characters and inform the controller of mode changes and of certain protocol events, such as resetting the

BCS. Using the control character table correctly allows the remainder of the block to be received without

interrupting software.

Up to eight control characters can be defined to inform the BISYNC controller that the end of the current

block is reached and whether a BCS is expected after the character. For example, the end-of-text character

(ETX) implies an end-of-block (ETB) with a subsequent BCS. An enquiry (ENQ) character designates an

end of block without a subsequent BCS. All the control characters are written into the data buffer. The

BISYNC controller uses a table of 16-bit entries to support control character recognition. Each entry

consists of the control character, an end-of-table bit (E), a BCS expected bit (B), and a hunt mode bit (H).

The RCCM entry defines classes of control characters that support masking option. The control character

table and RCCM are shown in Figure 23-2.

Offset from

SCC

x Base

123

0x42

—

CHARACTER1

0x44

—

CHARACTER2

0x46

—

CHARACTER3

0x48

—

CHARACTER4

0x4A

—

CHARACTER5

0x4D

—

CHARACTER6

0x4E

—

CHARACTER7

0x50

—

CHARACTER8

0x52

—

MASK VALUE(RCCM)

Figure 23-2. Control Character Table and RCCM

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