// bcc -ansi -Md -O iodump.c -o iodump.com

#define	uartBase	0x2e8
#define	uartClock	1843200		// Hz
#define	uartSpeed	115200		// bps
#define	uartDivisor	(uartClock / (uartSpeed * 16))

#define	RHR		(uartBase + 0x00)	// r
#define	THR		(uartBase + 0x00)	//  w
#define	IER		(uartBase + 0x01)	// rw
#define	ISR		(uartBase + 0x02)	// r
#define	FCR		(uartBase + 0x02)	//  w
#define	LCR		(uartBase + 0x03)	// rw
#define	MCR		(uartBase + 0x04)	// rw
#define	LSR		(uartBase + 0x05)	// r

#define	DLL		(uartBase + 0x00)	// rw
#define	DLM		(uartBase + 0x01)	// rw


unsigned char	in_b(unsigned short port)
{
#asm
	push	bp
	mov	bp, sp

	mov	dx, [bp + 4]

	in	al, dx

	pop	bp
#endasm
}

void	out_b(unsigned short port, unsigned char data)
{
#asm
	push	bp
	mov	bp, sp

	mov	dx, [bp + 4]
	mov	al, [bp + 6]

	out	dx, al

	pop	bp
#endasm
}

int	putchar(int c)
{
	while(!(in_b(LSR) & 0x20));		// wait for Tx ready
	out_b(THR, c);

	return c;
}

int	getchar(void)
{
	unsigned char	s, c;

	while (1) {
		s = in_b(LSR);			// get status
		if (s & 0x1f) {			// Rx ready
			c = in_b(RHR);		// read from FIFO
			if (!(s & 0x1e)) break;	// no error
		}
	}

	return c;
}

void	inituart(void)
{
	out_b(IER, 0x00);		// disable interrupt
	out_b(LCR, 0x80);		// set divisor
	out_b(DLM, 0xff);		// (avoid divisor=0)
	out_b(DLL, (uartDivisor >> 0) & 0xff);
	out_b(DLM, (uartDivisor >> 8) & 0xff);
	out_b(LCR, 0x03);		// data 8bit, stop 1bit, non-parity
	out_b(MCR, 0x03);		// RTS#, DTR# assert
	out_b(FCR, 0x07);		// FIFO enable and reset

	return;
}

void	putx1(unsigned char v)
{
	static	unsigned char	c[] = "0123456789ABCDEF";

	putchar(c[v & 0x0f]);
	return;
}

void	putx2(unsigned char v)
{
	putx1(v >> 4);
	putx1(v >> 0);
}

void	putx4(unsigned short v)
{
	putx2(v >> 8);
	putx2(v >> 0);
}

void	putx8(unsigned long v)
{
	putx4(v >> 16);
	putx4(v >> 0);
}

int	putstr(char *str)
{
	while (*str) putchar(*str++);

	return 0;
}

int	main(int argc, char *argv[])
{
	unsigned int	a;

	inituart();

	putstr("Press any key to start\n");
	getchar();

	a = 0;
	do {
		if (!(a % 16)) {
			putx4(a);
			putchar(':');
			putchar(' ');
		}

		putx2(in_b(a));
		putchar(' ');

		a++;
		if (!(a % 16)) {
			putchar('\n');
		}
	} while (a != 0);

	return 0;
}