MPC8280 datasheet(729/1386 Pages) FREESCALE

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SCC UART Mode

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

21-23

17. Initialize the RxBD. Assume the Rx buffer is at 0x0000_1000 in main memory. Write 0xB000 to

the RxBD[Status and Control], 0x0000 to RxBD[Data Length] (optional), and 0x0000_1000 to

RxBD[Buffer Pointer].

18. Initialize the TxBD. Assume the buffer is at 0x0000_2000 in main memory and contains sixteen

8-bit characters. Write 0xB000 to the TxBD[Status and Control], 0x0010 to TxBD[Data Length],

and 0x00002000 to TxBD[Buffer Pointer].

19. Write 0xFFFF to SCCE2 to clear any previous events.

20. Write 0x0003 to SCCM2 to allow the TX and RX interrupts.

21. Write 0x0040_0000 to the SIMR_L so SCC2 can generate a system interrupt. Initialize SIPNR_L

by writing 0xFFFF_FFFF to it.

22. Write 0x0000_0020 to GSMR_H2 to configure a small Rx FIFO width.

23. Write 0x0002_8004 to GSMR_L2 to configure 16

× sampling for transmit and receive, CTS and

CD to automatically control transmission and reception (DIAG bits), and the SCC for UART mode.

Notice that the transmitter (ENT) and receiver (ENR) have not been enabled yet.

24. Set PSMR2 to 0xB000 to configure automatic flow control using CTS, 8-bit characters, no parity,

1 stop bit, and asynchronous SCC UART operation.

25. Write 0x0002_8034 to GSMR_L2 to enable the transmitter and receiver. This ensures that ENT

and ENR are enabled last.

NOTE

After 16 bytes are sent, the transmit buffer is closed. Additionally, the

receive buffer is closed after 16 bytes are received. Data received after 16

bytes causes a busy (out-of-buffers) condition because only one RxBD is

prepared.

21.22 S-Records Loader Application

This section describes a downloading application that uses an SCC UART controller. The application

performs S-record downloads and uploads between a host computer and an intelligent peripheral through

a serial asynchronous line. S-records are strings of ASCII characters that begin with ‘S’ and end in an

end-of-line character. This characteristic is used to impose a message structure on the communication

between the devices. For flow control, each device can transmit XON and XOFF characters, which are not

part of the program being uploaded or downloaded.

For simplicity, assume that the line is not multidrop (no addresses are sent) and that each S-record fits into

a single buffer. Follow the basic UART initialization sequence above in Section 21.21, “SCC UART

Programming Example,” except allow for more and larger buffers and create the control character table as

described in Table 21-14.

MPC8280 Datasheet(PDF) 729 Page - Freescale Semiconductor, Inc