Header File: #include <FOSSIL.H>
Here is the API definition for access to the serial ports.
The @Chip-RTOS offers the Fossil API for serial port communication.
The Fossil standard uses software interrupt 0x14.
These functions provide
access to the @Chip-RTOS internal serial port driver for receiving and
sending data via the serial ports.
Here is a short description how the @Chip-RTOS internal serial port driver operates:
Each serial port has two software buffers (queues), one for data pending
transmission and one for storing received data bytes. The default size of
each queue is 1024 bytes. The size of these transmit
and receive queues are configurable via
Transfers between these software queues and the serial port hardware
are carried out by either Direct Memory Access (DMA) hardware or by
hardware interrupt (IRQ) driven software. By default, the available
DMA machines are applied to the serial port receivers. This configuration
reduces the likelihood of character loss at the receiver. This leaves the
serial port transmitters operating with hardware interrupt (IRQ) driven software.
Alternately, receivers can be configured for interrupt driven mode (IRQ receive mode)
with the CHIP.INI options,
which frees up the DMA device for other usage.
The DMA can be applied to transmitters with the SERIAL
The serial port hardware issues a signal to either software (IRQ hardware interrupt)
or to the DMA when ever the serial port transmit register is empty or a
receiver byte is ready. This signal initiates the next byte transfer
between the appropriate software queue and the hardware register, in or out. (This
discussion is slightly over simplified. The driver actually uses an
additional intermediate RAM buffer for DMA transfers.)
Note that the serial port hardware send/receive buffers are only one byte (four bytes)
deep on the SC1x (SC1x3/SC2x). So interrupt driven receivers (as opposed
to DMA driven) can easily lose characters, particularly at higher baud rates.
The serial ports may also be referred to as a UART (abbreviation for
"Universal Asynchronous Receiver/Transmitter").
For some useful comments see