MPC8280 datasheet(730/1386 Pages) FREESCALE

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SCC UART Mode

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

21-24

Freescale Semiconductor

To receive S-records, the core must wait for an RX interrupt, indicating that a complete S-record buffer

was received. Transmission requires assembling S-records into buffers and linking them to the TxBD

table; transmission can be paused when an XOFF character is received. This scheme minimizes the

number of interrupts the core receives (one per S-record) and relieves it from continually scanning for

control characters.

Table 21-14. UART Control Characters for S-Records Example

Character

Description

Line Feed

Both the E and R bits should be cleared. When an end-of-line character is received, the current buffer is

closed and made available to the core for processing. This buffer contains an entire S record that the

processor can now check and copy to memory or disk as required.

XOFF

E should be cleared; R should be set. Whenever the core receives a control-character-received (CCR)

interrupt and the RCCR contains XOFF, the software should immediately stop transmitting by setting

PSMR[FRZ]. This keeps the other station from losing data when it runs out of Rx buffers.

XON

XON should be received after XOFF. E should be cleared and R should be set. PSMR[FRZ] on the

transmitter should now be cleared. The CPM automatically resumes transmission of the serial line at the

point at which it was previously stopped. Like XOFF, the XON character is not stored in the receive buffer.

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