Starting IEC low-level code

I'm trying this code first in C. I may need to scrap it and go to assembly and follow Gadget's code more closely.

src/C256/iec.s

@@ -0,0 +1,85 @@
+;;;
+;;; Low-level support code for the IEC port
+;;;
+
+				.public sleep_20us
+				.public sleep_100us
+				.public sleep_300us
+				.public sleep_1ms
+
+#include "F256/iec_f256.h"
+
+;
+; Macros
+;
+
+;
+; Macro to set IEC output pins
+;
+; @param pins the bit masks for the pins to set
+;
+set_pins:		.macro pins
+				lda far:IEC_OUT
+				and #~(\pins)
+				sta far:IEC_OUT
+				.mend
+
+;
+; Macro to clear IEC output pins
+;
+; @param pins the bit masks for the pins to clear
+;
+clr_pins:		.macro pins
+				lda far:IEC_OUT
+				ora #(\pins)
+				sta far:IEC_OUT
+				.mend
+
+;
+; Macro to set and clear pins in one shot
+;
+; @param set_pins the bit masks for the pins to set
+; @param clr_pins the bit masks for the pins to clear
+;
+set_clr_pins:	.macro set_pins, clr_pins
+				lda far:IEC_OUT
+				and #~(\set_pins)
+				ora #(\clr_pins)
+				sta far:IEC_OUT
+				.mend
+
+read_pin:		.macro pin
+				pha
+				lda far:IEC_IN
+				bit #(\pin)
+				pla
+				.mend
+
+;
+; Routines
+;
+
+sleep_20us:		phx
+	            ldx #20
+_loop$       	dex
+				bne _loop$
+				plx
+				rtl
+            
+sleep_100us:	phx
+            	ldx #5
+_loop$	      	jsl sleep_20us
+				dex
+				bne _loop$
+				plx
+				rtl                
+
+sleep_300us:	jsl sleep_100us
+            	jsl sleep_100us
+            	jsl sleep_100us
+            	rtl
+            
+sleep_1ms:		jsl sleep_300us
+            	jsl sleep_300us
+            	jsl sleep_300us
+            	jmp sleep_100us

src/dev/iec_port.c

@@ -0,0 +1,307 @@
+/**
+ * @file iec_port.c
+ * @author your name (you@domain.com)
+ * @brief Implement the low level control code for the IEC port on the F256
+ * @version 0.1
+ * @date 2024-07-19
+ * 
+ * @copyright Copyright (c) 2024
+ * 
+ */
+
+#include <stdint.h>
+#include <calypsi/intrinsics65816.h>
+
+#include "F256/iec_f256.h"
+#include "errors.h"
+
+/**
+ * @brief Wait for 20 microseconds
+ * 
+ */
+static void sleep_20us() {
+	__asm(
+	    "   phx"
+        "   ldx ##20"
+		"1$ dex"
+        "   bne 1$"
+        "   plx"
+	);
+}
+
+/**
+ * @brief Wait for 100 microseconds
+ * 
+ */
+static void sleep_100us() {
+	__asm(
+		"   phx"
+		"   ldx #5"
+		"1$ jsl sleep_20us"
+		"   dex"
+		"   bne 1$"
+		"   plx"
+	);
+}
+
+/**
+ * @brief Wait for 300 microseconds
+ * 
+ */
+static void sleep_300us() {
+	sleep_100us();
+	sleep_100us();
+	sleep_100us();
+}
+
+/**
+ * @brief Wait for 1 millisecond
+ * 
+ */
+static void sleep_1ms() {
+	sleep_300us();
+	sleep_300us();
+	sleep_300us();
+}
+
+/**
+ * @brief Assert pins on the IEC port
+ * 
+ * @param pins mask bits of the pins to assert
+ */
+static void iec_assert(uint8_t pins) {
+	*IEC_OUT &= ~pins;
+}
+
+/**
+ * @brief Release pins on the IEC port
+ * 
+ * @param pins mask bits of the pins to release
+ */
+static void iec_release(uint8_t pins) {
+	*IEC_OUT |= pins;
+}
+
+/**
+ * @brief Assert and release pins in one transaction
+ * 
+ * @param assert_pins mask bits of pins to assert
+ * @param release_pins mask bits of pins to release
+ */
+static void iec_assert_release(uint8_t assert_pins, uint8_t release_pins) {
+	*IEC_OUT = (*IEC_OUT & ~assert_pins) | release_pins;
+}
+
+/**
+ * @brief Read a pin on the IEC port, given its mask bit
+ * 
+ * @param pin mask bit of the pin to read
+ * @return uint8_t 0 = pin released, 1 = pin asserted
+ */
+static uint8_t iec_read(uint8_t pin) {
+	uint8_t v1 = *IEC_IN;
+	uint8_t v2 = *IEC_IN;
+	while (v1 != v2)  {
+		v1 = v2;
+		v2 = *IEC_IN;
+	}
+	return ((v2 & pin == 0) ? 1 : 0);
+}
+
+static short iec_send_common(uint8_t data, bool eoi) {
+	sleep_300ms();
+
+	iec_release(IEC_PIN_CLK | IEC_PIN_DATA);
+
+	// Wait for the DATA line to be released by all the listeners
+	// NOTE: we may need to use Gadget's clever DATA hack
+	do {
+		sleep_20us();
+	} while(iec_read(IEC_PIN_DATA));
+
+	if (eoi) {
+		// If EOI, we wait until the listener ACKs the EOI
+		while (!iec_read(IEC_PIN_DATA)) ;
+
+		// Thgen wait for the DATA 
+		do {
+			sleep_20us();
+		} while(iec_read(IEC_PIN_DATA));
+	}
+
+	// Actually send the bits...
+
+	sleep_20us();
+	for (short bit = 0; bit < 8; bit++) {
+		iec_assert(IEC_PIN_CLOCK);
+		if (data & 0x01) {
+			iec_assert(IEC_PIN_DATA);
+		} else {
+			iec_release(IEC_PIN_DATA);
+		}
+		data = data >> 1;
+
+		sleep_20us();
+		sleep_20us();
+		iec_release(IEC_PIN_CLOCK);
+		sleep_20us();
+	}
+
+	iec_release(IEC_PIN_DATA);
+	iec_assert(IEC_PIN_CLK);
+
+	for (short count = 0; count < 50; count++) {
+		if (iec_read(IEC_PIN_DATA)) {
+			break;
+		}
+		sleep_20us();
+	}
+
+	return 0;
+}
+
+static short iec_atn_common(uint8_t data) {
+	__interrupt_state_t state = __get_interrupt_state();
+	__disable_interrupts;
+
+	iec_assert_release((IEC_PIN_ATN | IEC_PIN_CLK), IEC_PIN_DATA);
+	sleep_1ms();
+
+	if (iec_read(IEC_PIN_DATA)) {
+		iec_release(IEC_PIN_ATN);
+		__restore_interrupt_state(state);
+		return ERR_GENERAL;
+	}
+
+	short result = iec_send_common(data, false);
+	__restore_interrupt_state(state);
+	return result;
+}
+
+static short iec_atn_release(uint8_t data) {
+	iec_atn_common(data);
+	iec_release(IEC_PIN_ATN);
+	sleep_20us();
+	sleep_20us();
+	sleep_20us();
+	iec_release(IEC_PIN_CLK | IEC_PIN_DATA);
+}
+
+static uint8_t iec_read_b() {
+	bool is_eoi = false;
+	while(iec_read(IEC_PIN_CLK)) {
+		// TODO: detect EOI here
+		;
+	}
+
+	iec_release(IEC_PIN_DATA);
+
+	while(iec_read(IEC_PIN_CLK)) ;
+
+	uint8_t data = 0;
+	for (short count = 0; count < 8; count++) {
+		data = data >> 1;
+
+		while(iec_read(IEC_PIN_CLK)) ;
+		
+		if (iec_read(IEC_PIN_DATA)) {
+			data |= 0x80;
+		}
+
+		while(!iec_read(IEC_PIN_CLK)) ;
+	}
+
+	iec_assert(IEC_PIN_DATA);
+	sleep_20us();
+	iec_release(IEC_PIN_DATA);
+
+	if (eoi) {
+		// We have the last byte, wait for the talker to turn around the bus
+		while (iec_read(IEC_PIN_CLK)) ;
+
+		// Take back control of the bus
+		iec_assert(IEC_PIN_CLK);
+	}
+
+	return data;
+}
+
+/**
+ * @brief Send the TALK command to an IEC device
+ * 
+ * @param device the number of the IEC device to make a talker
+ */
+void iec_talk(uint8_t device) {
+	return iec_atn_common(IEC_CMD_TALK | (device & 0x0f));
+}
+
+/**
+ * @brief Send the secondary address for the talk command
+ * 
+ * @param channel the channel for the secondary address
+ */
+static void iec_talk_sa(uint8_t channel) {
+	iec_atn_release_release(channel & 0x0f);
+
+	// Turn around control of the bus to the talker
+	iec_assert(IEC_PIN_DATA);
+	iec_release(IEC_PIN_CLK);
+
+	// Wait for acknowledgement that we have a talker
+	while(!iec_read(IEC_PIN_CLK)) ;
+}
+
+/**
+ * @brief Send the UNTALK command
+ * 
+ */
+void iec_untalk() {
+	iec_atn_release(IEC_CMD_UNTALK);
+}
+
+/**
+ * @brief Send the UNLISTEN command
+ * 
+ */
+static void iec_unlisten() {
+	iec_atn_release(IEC_CMD_UNLISTEN);
+}
+
+/**
+ * @brief Retrieve the raw status string from an IEC device
+ * 
+ * @param device number of the IEC device to query
+ * @param buffer character buffer in which to write the status
+ * @param count the maximum number of bytes to fetch
+ */
+void iec_status(uint8_t device, char * buffer, short count) {
+	iec_talk(device);
+	iec_talk_sa(IEC_CMD_OPENCH | 0x0f);
+
+	// TODO: handle the EOI
+
+	for (short i = 0; i < count; i++) {
+		char c = iec_read_b();
+		buffer[i] = c;
+	}
+
+	iec_untalk();
+}
+
+/**
+ * @brief Initialize the IEC port
+ * 
+ * @return short 0 on success, a negative number indicates an error
+ */
+short iec_init() {
+	iec_assert_release(IEC_PIN_CLK, (IEC_PIN_ATN | IEC_PIN_DATA | IEC_PIN_SREQ));
+	sleep_1ms();
+	sleep_1ms();
+	sleep_1ms();
+
+	if (iec_read(IEC_PIN_ATN) || iec_read(IEC_PIN_SREQ)) {
+		return ERR_NOT_READY;
+	} else {
+		return 0;
+	}
+}

src/dev/iec_port.h

@@ -0,0 +1,33 @@
+/**
+ * @file iec_port.h
+ * @author your name (you@domain.com)
+ * @brief 
+ * @version 0.1
+ * @date 2024-07-22
+ * 
+ * @copyright Copyright (c) 2024
+ * 
+ */
+
+#ifndef __iec_port_h__
+#define __iec_port_h__
+
+#include <stdint.h>
+
+/**
+ * @brief Retrieve the raw status string from an IEC device
+ * 
+ * @param device number of the IEC device to query
+ * @param buffer character buffer in which to write the status
+ * @param count the maximum number of bytes to fetch
+ */
+extern void iec_status(uint8_t device, char * buffer, short count);
+
+/**
+ * @brief Initialize the IEC port
+ * 
+ * @return short 0 on success, a negative number indicates an error
+ */
+extern short iec_init();
+
+#endif

src/include/F256/iec_f256.h

@@ -7,7 +7,21 @@
 
 #include <stdint.h>
 
-#define IEC_BASE                ((volatile uint8_t *)0xf01680)
+#define IEC_CMD_LISTEN		0x20
+#define IEC_CMD_TALK		0x40
+#define IEC_CMD_OPENCH		0x60
+#define IEC_CMD_CLOSE		0xE0
+#define IEC_CMD_OPEN		0xF0
+#define IEC_CMD_UNLISTEN	0x3F
+#define IEC_CMD_UNTALK		0x5F
+
+#define IEC_IN				((volatile uint8_t *)0xf01680)
+#define IEC_OUT				((volatile uint8_t *)0xf01681)
+
+#define IEC_PIN_DATA		0x01
+#define IEC_PIN_CLK			0x02
+#define IEC_PIN_ATN			0x10
+#define IEC_PIN_SREQ		0x80
 
 // TODO: fill out with the actual registers