Freescale Semiconductor MPC8260 - Manual (Page 727)

SCC UART Mode
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Freescale Semiconductor 21-23
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 .
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.