Machine Library

I've created a library targeting the hardware specific aspects of programming the Sbc-3. I believe that it should work with the other boards from Mega Micros, but since I don't have access to anything but the Sbc-3, can't confirm that.

Note. if compiling for the 68000, you'll need to change the target cpu in src/stdenv.mk and src/lib/Makefile by changing the CPU macro.

To use the library, just include the following in your C sourcecode:

#include <machine.h>

Serial I/O

int _char_available(void);
char _getchar(void);
void _putchar(char c);

LED Control

There's a block of 10 leds (LD7 on the SBC3-b3), and six of them can be used for anything you like. Led1 is furthest from the cpu:

LED #	Used for
1	Indicates that the board is being powered via an external 5v supply.
2	Indicated that the board is being powered via the ATX power connector.
3	Connected to the ~RTS pin on the duart channel B.
4	Connected to the ~RTS pin on the duart channel A.
5	Available to user.
6	Available to user.
7	Available to user.
8	Available to user.
9	Available to user.
10	Available to user.

Two functions are provided, one to turn on a led, and another to turn it off.

void set_led(int lednum);
void clear_led(int lednum);

Where lednum is an integer in the range of 5 through to 10, as per the table above. Any other value will be silently ignored.

PI/T

void _pit_reset(void);
unsigned int _pit_get_counter(void);
unsigned int _pit_set_counter(unsigned int);
void pit_set_a(uint8_t val);
void pit_set_bits_a(uint8_t bits);
void pit_clear_bits_a(uint8_t bits);
void pit_set_b(uint8_t val);
void pit_set_bits_b(uint8_t bits);
void pit_clear_bits_b(uint8_t bits);

Compact Flash

void _cf_wait_busy(void);
void _cf_wait_data(void);
void cf_init(void);
int cf_identify(uint8_t drive_num, cf_info_t *info);
int cf_read(uint8_t drive_num, uint32_t sector, uint8_t *buffer);

Vectors and Interrupts

unsigned int *_get_vectors_base(void);
unsigned int get_isr_handler(int vector_number);
unsigned int set_isr_handler(int vector_number, void isr(void));

_get_vectors_base() return the contents of the ivr register on the 68030 or 0 on the 68000.

get_isr_handler returns the address of the handler currently configured to handle the exception specified by vector_number.

set_isr_handler() sets a handler for the exception specified by vector_number. It returns the address of the handler that it replaced, or 0xffffffff if the vector_number is out of range.

\(I^2c\) Bus

Safe Memory Access

int peek(uint8_t *addr);
int poke(uint8_t *addr, uint8_t val);

peek() attempts to read a byte from memory, returning the value read, or -1 if the read failed due to a Bus Error. Similarly, poke() attempts to write a byte to memory, returning -1 on a Bus Error.