path: root/avr/z80-if.c

/*
 * (C) Copyright 2014 Leo C. <erbl259-lmu@yahoo.de>
 *
 * SPDX-License-Identifier:	GPL-2.0
 */

/**
 *
 * Pin assignments
 *
 * | Z180-Sig   |   AVR-Port    | Dir   |
 * +------------+---------------+-------+
 * |    A0      | PA    0       |  O    |
 * |    A1      | PA    1       |  O    |
 * |    A2      | PA    2       |  O    |
 * |    A3      | PA    3       |  O    |
 * |    A4      | PA    4       |  O    |
 * |    A5      | PA    5       |  O    |
 * |    A6      | PA    6       |  O    |
 * |    A7      | PA    7       |  O    |
 * |    A8      | PC    0       |  O    |
 * |    A9      | PC    1       |  O    |
 * |    A10     | PC    2       |  O    |
 * |    A11     | PC    3       |  O    |
 * |    A12     | PC    4       |  O    |
 * |    A13     | PC    5       |  O    |
 * |    A14     | PC    6       |  O    |
 * |    A15     | PC    7       |  O    |
 * |    A16     | PE    2       |  O    |
 * |    A17     | PE    3       |  O    |
 * |    A18     | PE    4       |  O    |
 * |    D0      | PF    0       |  I/O  |
 * |    D1      | PF    1       |  I/O  |
 * |    D2      | PF    2       |  I/O  |
 * |    D3      | PF    3       |  I/O  |
 * |    D4      | PF    4       |  I/O  |
 * |    D5      | PF    5       |  I/O  |
 * |    D6      | PF    6       |  I/O  |
 * |    D7      | PF    7       |  I/O  |
 * |    RD      | PD    3       |  O    |
 * |    WR      | PD    2       |  O    |
 * |    MREQ    | PD    4       |  O    |
 * |    RST     | PD    5       |  O    |
 * |    BUSREQ  | PD    7       |  O    |
 * |    BUSACK  | PD    6       |  I    |
 * |
 * | Optional
 * +------------------------------------+
 * |    STEP    | PG    0       |  O    |
 * |    RUN     | PG    1       |  O    |
 * |    WAIT    | PG    2       |  I    |

 */


#include "z80-if.h"
#include <util/atomic.h>
#include "debug.h"
#include "config.h"
#include "env.h"


//#define P_ZCLK		PORTB
//#define ZCLK		5
//#define DDR_ZCLK	DDRB
#define P_MREQ		PORTD
#define MREQ		4
#define DDR_MREQ	DDRD
#define P_RD		PORTD
#define RD		3
#define P_WR		PORTD
#define WR		2
#define P_BUSREQ	PORTD
#define BUSREQ		7
#define DDR_BUSREQ	DDRD
#define P_BUSACK	PORTD
#define PIN_BUSACK	PIND
#define BUSACK		6
#define DDR_BUSACK	DDRD
#define P_RST		PORTD
#define PIN_RST		PIND
#define DDR_RST		DDRD
#define RST		5


#define P_DB		PORTF
#define PIN_DB		PINF
#define DDR_DB		DDRF

#define P_ADL		PORTA
#define P_ADH		PORTC
#define P_ADB		PORTE
#define PIN_ADB		PINE
#define DDR_ADL		DDRA
#define DDR_ADH		DDRC
#define DDR_ADB		DDRE

#define ADB_WIDTH	3
#define ADB_SHIFT	2
//#define ADB_PORT	PORTE


//#define Z80_O_ZCLK	SBIT(P_ZCLK, 5)
#define	Z80_O_MREQ	SBIT(P_MREQ, 4)
#define Z80_O_RD	SBIT(P_RD, 3)
#define Z80_O_WR	SBIT(P_WR, 2)
#define Z80_O_BUSREQ	SBIT(P_BUSREQ, 7)
//#define Z80_O_NMI	SBIT(P_NMI, )
#define Z80_O_RST	SBIT(P_RST, 5)
#define Z80_I_RST	SBIT(PIN_RST, 5)
#define Z80_I_BUSACK	SBIT(PIN_BUSACK, 6)
//#define Z80_I_HALT	SBIT(P_HALT, )

/* Optional */
#define P_RUN		PORTG
#define RUN			1
#define DDR_RUN		DDRG
#define P_STEP		PORTG
#define STEP		0
#define DDR_STEP	DDRG
#define P_WAIT		PORTG
#define WAIT		2
#define DDR_WAIT	DDRG
/* All three signals are on the same Port (PortG) */
#define PORT_SS		PORTG
#define DDR_SS		DDRG
#define PIN_SS		PING
#define	Z80_O_RUN	SBIT(PORT_SS, RUN)
#define	Z80_O_STEP	SBIT(PORT_SS, STEP)
#define	Z80_I_WAIT	SBIT(PORT_SS, WAIT)


#define BUS_TO 20


#define MASK(n)	((1<<(n))-1)
#define SMASK(w,s) (MASK(w) << (s))


static zstate_t zstate;
static volatile uint8_t timer;		/* used for bus timeout */
static bool reset_polarity;

/*---------------------------------------------------------*/
/* 10Hz timer interrupt generated by OC4A                  */
/*---------------------------------------------------------*/

ISR(TIMER5_COMPA_vect)
{

	uint8_t i = timer;

	if (i)
		timer = i - 1;
}

/*--------------------------------------------------------------------------*/


static void z80_addrbus_set_in(void)
{
	/* /MREQ, /RD, /WR: Input, no pullup */
	DDR_MREQ &= ~(_BV(MREQ) | _BV(RD) | _BV(WR));
	Z80_O_MREQ = 0;
	Z80_O_RD = 0;
	Z80_O_WR = 0;

	P_ADL = 0;
	DDR_ADL = 0;
	P_ADH = 0;
	DDR_ADH = 0;
	PIN_ADB = P_ADB & (MASK(ADB_WIDTH) << ADB_SHIFT);
	DDR_ADB = DDR_ADB & ~(MASK(ADB_WIDTH) << ADB_SHIFT);
}


static void z80_addrbus_set_out(void)
{
	/* /MREQ, /RD, /WR: Output and high */
	Z80_O_MREQ = 1;
	Z80_O_RD = 1;
	Z80_O_WR = 1;
	DDR_MREQ |= _BV(MREQ) | _BV(RD) | _BV(WR);

	DDR_ADL = 0xff;
	DDR_ADH = 0xff;
	DDR_ADB = DDR_ADB | (MASK(ADB_WIDTH) << ADB_SHIFT);
}


static void z80_dbus_set_in(void)
{
	DDR_DB = 0;
	P_DB = 0;
}


static void z80_dbus_set_out(void)
{
	DDR_DB = 0xff;
}

static void z80_reset_active(void)
{
	if (reset_polarity)
		Z80_O_RST = 1;
	else
		Z80_O_RST = 0;
}

static void z80_reset_inactive(void)
{
	if (reset_polarity)
		Z80_O_RST = 0;
	else
		Z80_O_RST = 1;
}

static void z80_reset_pulse(void)
{
	z80_reset_active();
	_delay_us(10);
	z80_reset_inactive();
}


void z80_setup_bus(void)
{
	ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {

		/* /ZRESET: Input, no pullup */
		DDR_RST &= ~_BV(RST);
		Z80_O_RST = 0;

		/* /BUSREQ: Output and high */
		Z80_O_BUSREQ = 1;
		DDR_BUSREQ |= _BV(BUSREQ);

		/* /BUSACK: Input, no pullup */
		DDR_BUSACK &= ~_BV(BUSACK);
		P_BUSACK &= ~_BV(BUSACK);

		z80_addrbus_set_in();
		z80_dbus_set_in();

		if (getenv_yesno(PSTR(ENV_SINGLESTEP))) {
			/* /RUN & /STEP: output, /WAIT: input */

			PORT_SS = (PORT_SS & ~_BV(RUN)) | _BV(STEP);
			DDR_SS = (DDR_SS & ~_BV(WAIT)) | _BV(RUN) | _BV(STEP);
		}

		reset_polarity = Z80_I_RST;
		z80_reset_active();
		DDR_RST |= _BV(RST);

		zstate = RESET;
	}

	/* Timer 5 */
	PRR1 &= ~_BV(PRTIM5);
	OCR5A = F_CPU / 1024 / 10 - 1;		  /* Timer: 10Hz interval (OC4A) */
	TCCR5B = (0b01<<WGM52)|(0b101<<CS40); /* CTC Mode, Prescaler 1024 */
	TIMSK5 = _BV(OCIE5A);				  /* Enable oca interrupt */

}


zstate_t z80_bus_state(void)
{
	return zstate;
}


static void z80_busreq_hpulse(void)
{
	z80_dbus_set_in();
	z80_addrbus_set_in();

#if 0
	ATOMIC_BLOCK(ATOMIC_FORCEON) {
		Z80_O_BUSREQ = 1;
		Z80_O_BUSREQ = 1;	/* 2 AVR clock cycles */
		Z80_O_BUSREQ = 0;	/* 2 AVR clock cycles */
	}
#endif

#if 1
	ATOMIC_BLOCK(ATOMIC_FORCEON) {
		Z80_O_BUSREQ = 1;

		do {
			if (Z80_I_BUSACK == 1)  {
				Z80_O_BUSREQ = 0;
				break;
			}
		} while (1);
	}
#endif

	if (zstate & ZST_ACQUIRED) {
		timer = BUS_TO;
		while (Z80_I_BUSACK == 1 && timer)
			;
		if (Z80_I_BUSACK == 0)
			z80_addrbus_set_out();
	}
}


/*

 +              |               |               |               |               |
    +   State   |     RESET     |  RESET_AQRD   |    RUNNING    | RUNNING_AQRD  |
       +        |               |               |               |               |
          +     |       0       |       1       |       2       |       3       |
Event        +  |               |               |               |               |
----------------+---------------+---------------+---------------+---------------+
                |               |               |               |               |
Reset           |       0       |       0       |       0       |       0       |
                |               |               |               |               |
                |               |               |               |               |
Request         |       1       |               |       3       |               |
                |               |               |               |               |
                |               |               |               |               |
Release         |               |       0       |               |       2       |
                |               |               |               |               |
                |               |               |               |               |
Run             |       2       |       3       |               |               |
                |               |               |               |               |
                |               |               |               |               |
Restart         |               |               |       2       |       3       |
                |               |               |               |               |
                |               |               |               |               |
M_Cycle         |               |               |               |       3       |
                |               |               |               |               |
                |               |               |               |               |
*/

zstate_t z80_bus_cmd(bus_cmd_t cmd)
{
	switch (cmd) {

	case Reset:
		z80_dbus_set_in();
		z80_addrbus_set_in();
		z80_reset_active();
		Z80_O_BUSREQ = 1;
		zstate = RESET;
		break;

	case Request:
		switch (zstate) {
		case RESET:
			Z80_O_BUSREQ = 0;
			z80_reset_inactive();
			timer = BUS_TO;
			while (Z80_I_BUSACK == 1 && timer)
				;
			if (Z80_I_BUSACK == 0) {
				z80_addrbus_set_out();
				zstate = RESET_AQRD;
			} else {
				z80_reset_active();
				Z80_O_BUSREQ = 1;
			}
			break;

		case RUNNING:
			Z80_O_BUSREQ = 0;
			timer = BUS_TO;
			while (Z80_I_BUSACK == 1 && timer)
				;
			if (Z80_I_BUSACK == 0) {
				z80_addrbus_set_out();
				zstate = RUNNING_AQRD;
			} else {
				Z80_O_BUSREQ = 1;
			}
			break;

		default:
			break;
		}
		break;

	case Release:
		switch (zstate) {
		case RESET_AQRD:
			z80_dbus_set_in();
			z80_addrbus_set_in();
			z80_reset_active();
			Z80_O_BUSREQ = 1;
			zstate = RESET;
			break;
		case RUNNING_AQRD:
			z80_dbus_set_in();
			z80_addrbus_set_in();
			Z80_O_BUSREQ = 1;
			zstate = RUNNING;
			break;
		default:
			break;
		}
		break;

	case Run:
		switch (zstate) {
		case RESET:
			z80_reset_inactive();
			zstate = RUNNING;
			break;

		case RESET_AQRD:
			z80_dbus_set_in();
			z80_addrbus_set_in();
			z80_reset_pulse();
			z80_addrbus_set_out();
			zstate = RUNNING_AQRD;
			break;
		default:
			break;
		}
		break;

	case Restart:
		switch (zstate) {
		case RUNNING:
		case RUNNING_AQRD:
			z80_reset_pulse();
			break;
		default:
			break;
		}
		break;

	case M_Cycle:
		switch (zstate) {
		case RUNNING_AQRD:
			z80_busreq_hpulse();	/* TODO: */
			break;
		default:
			break;
		}
	}
	return zstate;
}


/*--------------------------------------------------------------------------*/

static
//inline __attribute__ ((always_inline))
void z80_setaddress(uint32_t addr)
{
	P_ADL = addr;
	P_ADH = (addr & 0xff00) >> 8;
	PIN_ADB = (((addr >> 16) << ADB_SHIFT) ^ P_ADB) & MASK(ADB_WIDTH) << ADB_SHIFT;
}

void z80_write(uint32_t addr, uint8_t data)
{
	z80_setaddress(addr);
	Z80_O_MREQ = 0;
	z80_dbus_set_out();
	P_DB = data;
	P_DB = data;
	Z80_O_WR = 0;
	Z80_O_WR = 0;
	Z80_O_WR = 1;
	Z80_O_MREQ = 1;
}

uint8_t z80_read(uint32_t addr)
{
	uint8_t data;

	z80_setaddress(addr);
	Z80_O_MREQ = 0;
	z80_dbus_set_in();
	Z80_O_RD = 0;
	Z80_O_RD = 0;
	Z80_O_RD = 0;
	data = PIN_DB;
	Z80_O_RD = 1;
	Z80_O_MREQ = 1;

	return data;
}


void z80_memset(uint32_t addr, uint8_t data, uint32_t length)
{
	z80_dbus_set_out();
	Z80_O_MREQ = 0;
	P_DB = data;
	while(length--) {
		z80_setaddress(addr++);
		Z80_O_WR = 0;
		Z80_O_WR = 0;
		Z80_O_WR = 1;
	}
	Z80_O_MREQ = 1;
}

void z80_write_block_P(const FLASH uint8_t *src, uint32_t dest, uint32_t length)
{
	uint8_t data;

	z80_dbus_set_out();
	Z80_O_MREQ = 0;
	while(length--) {
		z80_setaddress(dest++);
		data = *src++;
		P_DB = data;
		P_DB = data;
		Z80_O_WR = 0;
		Z80_O_WR = 0;
		Z80_O_WR = 1;
	}
	Z80_O_MREQ = 1;
}

void z80_write_block(const uint8_t *src, uint32_t dest, uint32_t length)
{
	uint8_t data;

	z80_dbus_set_out();
	Z80_O_MREQ = 0;
	while(length--) {
		z80_setaddress(dest++);
		data = *src++;
		P_DB = data;
		P_DB = data;
		Z80_O_WR = 0;
		Z80_O_WR = 0;
		Z80_O_WR = 1;
	}
	Z80_O_MREQ = 1;
}

void z80_read_block (uint8_t *dest, uint32_t src, size_t length)
{
	uint8_t data;

	Z80_O_MREQ = 0;
	z80_dbus_set_in();
	while(length--) {
		z80_setaddress(src++);
		Z80_O_RD = 0;
		Z80_O_RD = 0;
		Z80_O_RD = 0;
		data = PIN_DB;
		Z80_O_RD = 1;
		*dest++ = data;
	}
	Z80_O_MREQ = 1;
}


/*
  0179'                         rx.bs_mask:	ds	1		; (buf_len - 1)
  017A'                         rx.in_idx:	ds	1		;
  017B'                         rx.out_idx:	ds	1		;
  017C'                         rx.buf:		ds	rx.buf_len	;
  018B'                         rx.buf_end	equ	$-1		; last byte (start+len-1)

  018C'                         tx.bs_mask:	ds	1		; (buf_len - 1)
  018D'                         tx.in_idx:	ds	1		;
  018E'                         tx.out_idx:	ds	1		;
  018F'                         tx.buf:		ds	tx.buf_len 	;
  019E'                         tx.buf_end	equ	$-1		; last byte
*/


typedef struct __attribute__((packed)) {
	uint8_t mask;
	uint8_t in_idx;
	uint8_t out_idx;
	uint8_t buf[];
} zfifo_t;



#define FIFO_BUFSIZE_MASK	-3
#define FIFO_INDEX_IN		-2
#define FIFO_INDEX_OUT		-1


static struct {
	uint32_t base;
	uint8_t idx_out,
		idx_in,
		mask;
	} fifo_dsc[NUM_FIFOS];


void z80_memfifo_init(const fifo_t f, uint32_t addr)
{
	fifo_dsc[f].base = addr;


	if (addr != 0) {
		z80_bus_cmd(Request);
		fifo_dsc[f].mask = z80_read(addr + FIFO_BUFSIZE_MASK);
		fifo_dsc[f].idx_in = z80_read(addr + FIFO_INDEX_IN);
		fifo_dsc[f].idx_out = z80_read(addr + FIFO_INDEX_OUT);
		z80_bus_cmd(Release);

		if (fifo_dsc[f].idx_in != 0 || fifo_dsc[f].idx_out != 0) {
			DBG_P(1, "## z80_memfifo_init: %i, %lx, in: %.2x, out: %.2x, mask: %.2x\n",
					f, addr, fifo_dsc[f].idx_in, fifo_dsc[f].idx_out, fifo_dsc[f].mask);
		}
	}
}


int z80_memfifo_is_empty(const fifo_t f)
{
	int rc = 1;

	if (fifo_dsc[f].base != 0) {

		uint32_t adr = fifo_dsc[f].base + FIFO_INDEX_IN;
		uint8_t idx;

		z80_bus_cmd(Request);
		idx = z80_read(adr);
		z80_bus_cmd(Release);
		rc = idx == fifo_dsc[f].idx_out;
	}

	return rc;
}

int z80_memfifo_is_full(const fifo_t f)
{
	int rc = 0;

	if (fifo_dsc[f].base != 0) {
		z80_bus_cmd(Request);
		rc = ((fifo_dsc[f].idx_in + 1) & fifo_dsc[f].mask)
			== z80_read(fifo_dsc[f].base+FIFO_INDEX_OUT);
		z80_bus_cmd(Release);
	}
	return rc;
}


uint8_t z80_memfifo_getc_wait(const fifo_t f)
{
	uint8_t rc, idx;

	while (z80_memfifo_is_empty(f))
		;

	z80_bus_cmd(Request);
	idx = fifo_dsc[f].idx_out;
	rc = z80_read(fifo_dsc[f].base+idx);
	fifo_dsc[f].idx_out = ++idx & fifo_dsc[f].mask;
	z80_write(fifo_dsc[f].base+FIFO_INDEX_OUT, fifo_dsc[f].idx_out);
	z80_bus_cmd(Release);

	return rc;
}

int z80_memfifo_getc(const fifo_t f)
{
	int rc = -1;

	if (fifo_dsc[f].base != 0) {
		uint8_t idx = fifo_dsc[f].idx_out;
		z80_bus_cmd(Request);
		if (idx != z80_read(fifo_dsc[f].base + FIFO_INDEX_IN)) {
			rc = z80_read(fifo_dsc[f].base+idx);
			fifo_dsc[f].idx_out = ++idx & fifo_dsc[f].mask;
			z80_write(fifo_dsc[f].base+FIFO_INDEX_OUT, fifo_dsc[f].idx_out);
		}
		z80_bus_cmd(Release);
	}

	return rc;
}


void z80_memfifo_putc(fifo_t f, uint8_t val)
{
	int idx;

	while (z80_memfifo_is_full(f))
		;

	z80_bus_cmd(Request);
	idx = fifo_dsc[f].idx_in;
	z80_write(fifo_dsc[f].base+idx, val);
	fifo_dsc[f].idx_in = ++idx & fifo_dsc[f].mask;
	z80_write(fifo_dsc[f].base+FIFO_INDEX_IN, fifo_dsc[f].idx_in);
	z80_bus_cmd(Release);
}