IPC@CHIP Documentation - SC12 @CHIP-RTOS V1.10

IPC@CHIP Documentation Index
FOSSIL
Fossil API - SC12 @CHIP-RTOS V1.10
Here is the API definition for access to the COM and EXT 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 chip.ini entries.
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 two available DMA
machines are applied to the two serial port receivers. This configuration reduces the likelihood of character loss
at the receiver. This leaves the two 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 SEND_DMA option.
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 deep. So interrupt driven receivers (as
opposed to DMA driven) can easily lose characters, particularly at higher baud rates.
The COM / EXT serial ports may also be referred to as a UART (abbreviation for "Universal Asynchronous
Receiver/Transmitter").
For some useful comments see Programming notes
New in version 1.10B: Install a user callback function
New in version 1.10B: Enable/Disable UART receiver
New in version 1.10B: Enable/Disable UART transmitter
● Interrupt_0x14_function_0x00:_Set baud rate
● Interrupt_0x14_function_0x01:_Put byte in output buffer, wait if needed.
● Interrupt_0x14_function_0x02:_Get a byte from the serial port, wait if none available.
● Interrupt_0x14_function_0x03:_Status request
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