Motorola MPC8260 - Manual (Page 607)

MOTOROLA Chapter 20. SCC UART Mode 20-23
Part IV. Communications Processor Module
15. Write CHARACTER1Ð8 with 0x8000. They are not used.
16. Write RCCM with 0xC0FF. It is not used.
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 SMC1 can generate a system interrupt.
Initialize SIPNR_L by writing 0xFFFF_FFFF to it.
22. Write 0x0000_0020 to GSMR_H2 to conÞgure a small Rx FIFO width.
23. Write 0x0002_8004 to GSMR_L2 to conÞgure 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 conÞgure automatic ßow 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 that 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.
20.22 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 ÔSÕ and end in an end-of-line character. This characteristic is used
to impose a message structure on the communication between the devices. For ßow 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 Þts into a single buffer. Follow the basic UART initialization sequence above in
Section 20.21, ÒSCC UART Programming Example,Ó except allow for more and larger
buffers and create the control character table as described in Table 20-14.