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Chapter 4 Software Development
page 4-28
For further details on these components, refer to the MSM6657 Family User's Manual.
Serial port (SIO0): Chapter 12
Internal timer: Chapter 8, page 9 and following
The source code file stdrw573.c sets up the serial port for these functions using the following steps
between the start and end comments for port and timer setup.
(1) Configure timer 3 for use as baud rate generator (BRG)
The serial port used for standard I/O derives its baud rate from the MSM66Q573 internal timer
3 overflow signal. The source code file stdrw573.c contains the settings for producing a 38,400-
b/s baud rate from the JOB60851 board's 24-MHz system clock.
(2) Configure serial port
All serial ports have registers for controlling operation. SIO0 has four such registers.
(a) SIO0 Transmit Control Register
This register specifies the data format for transmitting data and enables or disables the
relevant interrupts. The source code file stdrw573.c uses the following settings.
Word size 8 bits
Stop bits 2
Parity check None
Transmit buffer empty interrupt Enabled
Transmission end interrupt Enabled
(b) SIO0 Receive Control Register
This register specifies the data format for receiving and enables or disables the relevant
interrupts. The source code file stdrw573.c uses the following settings.
Word size 8 bits
Baud rate clock Timer 3
Parity check None
Receive end interrupt Enabled
SIO0 receive Enabled
(c) SIO0 Receive/Transmit Buffer Register
This 8-bit register holds the transfer data. It is actually two separate registers differentiated
by access. Writing to it writes to the transmit buffer. Reading from it reads from the receive
buffer.
(d) SIO0 Status Register
This status register gives the error status at the end of transmit/receive operations and the
running status during such operations. Note that the hardware does not reset this register, so
the user application program must do so before using the serial port.
Framing error flag "0"
Overrun error flag "0"
Parity error flag "0"
Transmit buffer empty flag "0"
Transmit end interrupt flag "0"