Книга: Advanced PIC Microcontroller Projects in C

9.9 PIC18F258 Microcontroller

Later in this chapter the PIC18F258 microcontroller is used in a CAN bus–based project. This section describes this microcontroller and its operating principles with respect to its built-in CAN bus. The principles here are in general applicable to other PIC microcontrollers with CAN modules.

The PIC18F258 is a high performance 8-bit microcontroller with integrated CAN module. The device has the following features:

• 32K flash program memory

• 1536 bytes RAM data memory

• 256 bytes EEPROM memory

• 22 I/O ports

• 5-channel 10-bit A/D converters

• Three timers/counters

• Three external interrupt pins

• High-current (25mA) sink/source

• Capture/compare/PWM module

• SPI/I?C module

• CAN 2.0A/B module

• Power-on reset and power-on timer

• Watchdog timer

• Priority level interrupts

• DC to 40MHz clock input

• 8?8 hardware multiplier

• Wide operating voltage (2.0V to 5.5V)

• Power-saving sleep mode

The features of the PIC18F258 microcontroller’s CAN module are as follows:

• Compatible with CAN 1.2, CAN 2.0A, and CAN 2.0B

• Supports standard and extended data frames

• Programmable bit rate up to 1Mbit/s

• Double-buffered receiver

• Three transmit buffers

• Two receive buffers

• Programmable clock source

• Six acceptance filters

• Two acceptance filter masks

• Loop-back mode for self-testing

• Low-power sleep mode

• Interrupt capabilities

The CAN module uses port pins RB3/CANRX and RB2/CANTX for CAN bus receive and transmit functions respectively. These pins are connected to the CAN bus via an MCP2551-type CAN bus transceiver chip.

The PIC18F258 microcontroller supports the following frame types:

• Standard data frame

• Extended data frame

• Remote frame

• Error frame

• Overload frame

• Interframe space

A node uses filters to decide whether or not to accept a received message. Message filtering is applied to the whole identifier field, and mask registers are used to specify which bits in the identifier the filters should examine.

The CAN module in the PIC18F258 microcontroller has six modes of operation:

• Configuration mode

• Disable mode

• Normal operation mode

• Listen-only mode

• Loop-back mode

• Error recognition mode

Оглавление книги