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ebe99f Bob Green 2026-03-19 08:31:29
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# Machine Library
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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](https://mega-micros.co.uk/index.htm), but since I don't have access to anything but the Sbc-3, can't confirm that.
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dca070 Bob Green 2026-05-21 09:36:22
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::: info
b51540 Bob Green 2026-05-21 09:35:14
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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.
dca070 Bob Green 2026-05-21 09:36:22
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:::
ebe99f Bob Green 2026-03-19 08:31:29
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To use the library, just include the following in your C sourcecode:
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```c
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#include <machine.h>
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```
2a20d4 Bob Green 2026-03-21 15:03:23
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## Serial I/O
b26e81 Bob Green 2026-03-21 15:10:58
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```C
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int _char_available(void);
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char _getchar(void);
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void _putchar(char c);
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```
9601f3 Bob Green 2026-05-27 09:23:37
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::: info
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Note. The xr68681 is clocked at 7.3728MHz, meaning you'll get double the baud rate listed in the data sheet as the datasheet assumes ha;f that rate. It will also affect the internal counter when it's clocked by the external clock.
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:::
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b26e81 Bob Green 2026-03-21 15:10:58
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2a20d4 Bob Green 2026-03-21 15:03:23
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## LED Control
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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:
d90362 Bob Green 2026-03-21 15:03:37
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2a20d4 Bob Green 2026-03-21 15:03:23
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| LED # | Used for |
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|:------|:---------|
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| 1 | Indicates that the board is being powered via an external 5v supply. |
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| 2 | Indicated that the board is being powered via the ATX power connector. |
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| 3 | Connected to the ~RTS pin on the duart channel B. |
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| 4 | Connected to the ~RTS pin on the duart channel A. |
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| 5 | Available to user. |
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| 6 | Available to user. |
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| 7 | Available to user. |
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| 8 | Available to user. |
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| 9 | Available to user. |
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| 10 | Available to user. |
91e139 Bob Green 2026-03-21 15:06:40
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Two functions are provided, one to turn on a led, and another to turn it off.
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```C
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void set_led(int lednum);
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void clear_led(int lednum);
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```
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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.
0c5486 Bob Green 2026-03-24 15:10:57
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b69dc8 Bob Green 2026-03-24 15:11:57
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## PI/T
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```C
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void _pit_reset(void);
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unsigned int _pit_get_counter(void);
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unsigned int _pit_set_counter(unsigned int);
3f2fd6 Bob Green 2026-05-27 08:42:03
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void pit_set_a(uint8_t val);
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void pit_set_bits_a(uint8_t bits);
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void pit_clear_bits_a(uint8_t bits);
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void pit_set_b(uint8_t val);
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void pit_set_bits_b(uint8_t bits);
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void pit_clear_bits_b(uint8_t bits);
b69dc8 Bob Green 2026-03-24 15:11:57
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```
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898676 Bob Green 2026-05-27 09:23:06
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::: info
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Note. The PI/T is clocked at 10.0MHz
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:::
0c5486 Bob Green 2026-03-24 15:10:57
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## Compact Flash
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```C
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void _cf_wait_busy(void);
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void _cf_wait_data(void);
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void cf_init(void);
910d81 Bob Green 2026-05-21 09:58:31
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int cf_identify(uint8_t drive_num, cf_info_t *info);
0c5486 Bob Green 2026-03-24 15:10:57
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int cf_read(uint8_t drive_num, uint32_t sector, uint8_t *buffer);
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```
d83b67 Bob Green 2026-03-24 15:21:18
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## Vectors and Interrupts
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```C
9463ec Bob Green 2026-03-24 15:22:39
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unsigned int *_get_vectors_base(void);
fc90ec Bob Green 2026-03-29 13:27:43
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unsigned int get_isr_handler(int vector_number);
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unsigned int set_isr_handler(int vector_number, void isr(void));
d83b67 Bob Green 2026-03-24 15:21:18
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```
910d81 Bob Green 2026-05-21 09:58:31
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1e0c28 Bob Green 2026-05-21 09:47:07
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`_get_vectors_base()` return the contents of the `ivr` register on the 68030 or 0 on the 68000.
41d04d Bob Green 2026-05-21 09:47:20
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1e0c28 Bob Green 2026-05-21 09:47:07
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`get_isr_handler` returns the address of the handler currently configured to handle the exception specified by `vector_number`.
41d04d Bob Green 2026-05-21 09:47:20
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f80b2d Bob Green 2026-05-21 09:49:31
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`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.
633040 Bob Green 2026-03-24 15:33:07
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f01b84 Bob Green 2026-03-24 15:41:57
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## `$I^2c$` Bus
633040 Bob Green 2026-03-24 15:33:07
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```C
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```
398ef5 Bob Green 2026-05-21 09:41:14
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## Safe Memory Access
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```C
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int peek(uint8_t *addr);
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int poke(uint8_t *addr, uint8_t val);
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```
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`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.