Merge branch 'dev'

Author: olivierjan

.gitignore

@@ -0,0 +1,4 @@
+
+.DS_Store
+.gitattributes
+.vscode

6502-SBC-using-Teensy.ino

@@ -1,27 +1,42 @@
-/*
-Bus Access system
-Access 65C02 address and databus on 24 Teensy Pins
-Start simulate some memory for 65c02 to Read/Write.
-*/
+//
+// TEENSY 65C02 
+// 
+// Access 65C02 address and databus using Teensy 3.6(3.3v) or 3.5 (5v)
+// Can simulate RAM, ROM and ACIA (6551 or 6850)
+// Provide access to all pins. 
+
 
 #include "SBC.h"
 
+// ROM image declared as a C Array.
+// Can be easily created from a real ROM image using srec_cat  
+// http://srecord.sourceforge.net/man/man1/srec_cat.html
+
 #ifdef ROMEMU
   #include "rom.h"
 #endif
 
 
 // Declare the Pins to use
 
+// Bus Pins (DATA and ADDRESS)
+// As the Teensy doens't expose 16 consecutive PINS attached to the same PORT
+// we need to split the Address bus over two different PORTS
+
+byte dataPins[] = {5,21,20,6,8,7,14,2};         // Data Bus
+byte addressHPins [] = {30,29,1,0,18,19,17,16}; // Address Bus High byte
+byte addressLPins[]={12,11,13,10,9,23,22,15};   // Address Bus Low byte
+
+// Variable declarations 
 
-byte dataPins[] = {2,14,7,8,6,20,21,5};         // Data Bus
-byte addressHPins [] = {16,17,19,18,0,1,29,30}; // Address Bus High byte
-byte addressLPins[]={15,22,23,9,10,13,11,12};   // Address Bus Low byte
 uint8_t chipEnable;                             // RAM, ROM or Serial to access
+
 #ifdef DEBUG
-byte databyte=0;
+byte databyte=0;              
 uint16_t savedaddress=0;
 #endif
+
+
 // Declare global variables
 // Must be volatile to avoid any compiler optimization
 
@@ -31,50 +46,98 @@ volatile boolean rw;
 volatile byte ACIAStatus;
 volatile uint16_t address;
 
+// If RAM emulation is required 
+// declare a corresponding array
+
 #ifdef RAMEMU
-  byte mem[RAMSIZE];  // declare RAM as a byte array.
+   byte mem[RAMSIZE];  // declare RAM as a byte array.
 #endif
 
 // Redefine yield() as the default one is useless and waste time.
+// This is required to achieve a descent speed
+
 void yield(){}
 
 void setup() {
 
   Serial.begin(0);                // Start the serial port
+  
+  #ifdef DEBUG
+  Serial.print("Bringing RESET LOW\n");
+  #endif
+
+  // First thing, let's bring reset LOW 
+  // This will stall the 6502 while we Initialize
+
+  pinMode(RESETPIN, OUTPUT);
+  digitalWrite(RESETPIN,LOW);     // Bring the RESET LOW to get the 6502
+                                  // in a reset state
 
   // Set all pins to their initial state.
   #ifdef DEBUG
     delay(2000);
     #ifdef RAMEMU
     Serial.print("RAM Emulation\n");
     #endif
-
     #ifdef ROMEMU
     Serial.print("ROM Emulation\n");
     #endif
-
     #ifdef ACIA6551
     Serial.print("6551 ACIA Emulation\n");
     #endif
-
     #ifdef ACIA6850
     Serial.print("6850 ACIA Emulation\n");
     #endif
-
+    #ifdef BARECPU
+    Serial.print("CPU Only\n");
+    #endif
     Serial.print("Initializing PINs\n");
-  #endif 
+  #endif
+
+  // Initialize Data and Address BUSs to Input
+  
   for (int i=0;i<8;i++) {
     pinMode(dataPins[i],INPUT);               //Ensure we're not writing to the Bus
     pinMode(addressLPins[i],INPUT_PULLDOWN);
     pinMode(addressHPins[i],INPUT_PULLDOWN);
   }
 
+  // Initialize R/W' and PHI2 
+
   pinMode(RWPIN, INPUT);
   pinMode(CLOCKPIN, OUTPUT);
-  pinMode(RESETPIN, OUTPUT);
+  
+  // With a bare CPU we need to drive these pins high.
+  // And SO LOW
+  // On a real SBC, this should be done by the circuit.
+
+  #ifdef BARECPU
+  pinMode(BEPIN, OUTPUT);
+  pinMode(RDYPIN, OUTPUT);
+  pinMode(NMIPIN, OUTPUT);
+  pinMode(IRQPIN, OUTPUT);
+  pinMode(MLPIN, INPUT);
+  pinMode(VPPIN, INPUT);
+  pinMode(SYNCPIN, INPUT);
+  pinMode(SOPIN,OUTPUT);
+  digitalWrite(BEPIN,HIGH);
+  digitalWrite(RDYPIN,HIGH);
+  digitalWrite(IRQPIN,HIGH);
+  digitalWrite(NMIPIN,HIGH);
+  digitalWrite(SOPIN,LOW);
+  #endif
+
+  // With a CPU on its own circuit we just want to read what happens.
+
+  #ifndef BARECPU
+  pinMode(BEPIN, INPUT);
+  pinMode(RDYPIN, INPUT);
+  pinMode(NMIPIN, INPUT);
+  pinMode(IRQPIN, INPUT);
+  #endif
 
   #ifdef DEBUG
-  Serial.print("Initializing varialbles\n");
+  Serial.print("Initializing variables\n");
   #endif
 
   // Initialize some variables
@@ -83,13 +146,9 @@ void setup() {
   chipEnable=0x0;
   rw=true;
 
-  #ifdef DEBUG
-  Serial.print("Bringing RESET LOW\n");
-  #endif
 
-  digitalWrite(RESETPIN,LOW);     // Bring the RESET LOW to get the 6502
-                                  // in a reset state
-
+  
+  
 #ifdef RAMEMU
   #ifdef DEBUG
   Serial.print("Initializing RAM\n");
@@ -104,20 +163,30 @@ void setup() {
   #endif
 
   digitalWrite(RESETPIN,HIGH);    // Release RESET and start working
-  
-  Serial.print("Starting SBC....\n");
+  Serial.print("Starting Teensy 65C02....\n");
 }
 
 
 void loop(){
 
-  GPIOA_PDOR &=0x0000;              // Bring Clock LOW to start Phase 1
-  for (i=0; i< WAITCYCLE; i++){}    // Keep Phase 1 LOW
+  
+  // Start the loop by bring Clock low and up again
+  // Duration of PHI1 (Clock low) is defined by WAITCYCLE
+
+  GPIOA_PDOR &=~(1<<13);            // Bring Clock LOW to start Phase 1
+                                    // Clock is on PIN 13 of PORT A
+
+  for (i=0; i< WAITCYCLE; i++){}    // Keep Phase 1 LOW for WAITCYCLES
+
   GPIOA_PDOR |=1<<13;               // Bring Clock HIGH to start Phase 2
 
+  // Read the Address BUSs
 
   addressL = GPIOC_PDIR;                  // Read the Address Bus Low byte
   addressH = GPIOB_PDIR;                  // Read the Address Bus High byte
+
+  // PORT B doesn't have 4 consecutive Pins so we need to concatenate
+
   addressH |= (GPIOB_PDIR >> 12) & 0xF0;  // Shift the register right by 12 bits
                                           // to get bits 16,17,18 and 19
                                           // in position 4,5,6 and 7.
@@ -129,27 +198,32 @@ void loop(){
   savedaddress=address;                           // Saving original address for DEBUG as it's modified for ROM access. 
   #endif
 
+  // Address decoding
+
   if (address < RAMSIZE) { 
         chipEnable=RAMENABLE;
       } else  if (address >= ROMADDRESS) {
         chipEnable=ROMENABLE;
       } else if (address >= ACIADDRESS) {
         chipEnable=ACIAENABLE;
       }
+
+  
   rw=(GPIOA_PDIR>>12)&0x1;                  // Check if it's a Write Cycle
                                             // or Read Cycle
+  
+  // If it's a READ Cycle, we need to reconfigure DATA Pins to OUTPUT
   GPIOD_PDDR=(rw) ? GPIOOUTPUT : GPIOINPUT; // Configure PIN direction.
 
 
-
+  // Based on Address decoding, now is time to taje appropriate actions.
   switch (chipEnable) {
 
-
-#if defined ACIA6551 || defined ACIA6850
+  #if defined ACIA6551 || defined ACIA6850
     case ACIAENABLE:
       if (rw) {
         if (address == ACIADATA){           // CPU wants to get data
-          GPIOD_PDOR=Serial.read() ;        // Send what's in buffer (CPU should have checked buffer ia not empty)
+          GPIOD_PDOR=Serial.read() ;        // Send what's in buffer (CPU should have checked buffer is not empty)
         } else if (address == ACIASTATUS) { // CPU Wants to check buffer status
           GPIOD_PDOR=(Serial.available()>0) ? (RDRFBIT | TDREBIT) : TDREBIT;  // We only check if read buffer is empty.
         }
@@ -160,7 +234,7 @@ void loop(){
         // We simply ignore the case where we receive config /Control/Reset byte for ACIA.
       }
       break;
-#endif
+  #endif
 
 
 #ifdef ROMEMU   
@@ -184,6 +258,7 @@ void loop(){
   }
   #ifdef DEBUG
   databyte=(rw) ? GPIOD_PDOR : GPIOD_PDIR;
+
   Serial.print(savedaddress,HEX);
   Serial.print("\t");
   Serial.print(rw);

README.md

@@ -1,6 +1,6 @@
 # SBC (for Teensy 3.6)
 
-This codes uses a Teensy to emulate hardware of a **6502** based computer apart from CPU itself.
+This codes uses a Teensy to emulate hardware of a **65C02** based computer apart from CPU itself.
 The following parts can be emulated :
 
  - Clock (mandatory)
@@ -24,7 +24,7 @@ Edit `SBC.h` and `#define` which part are to be emulated by commenting out the u
 > 3. If you emulate a component, make sure a real IC is not actually connected, as both Teensy and the IC will put data on the bus at the same time !
 
 ### ROM configuration
-If you emulate a ROM, provide it as a C Array in a file called `rom.h`. Two ROMs are provided here:
+If you emulate a ROM, provide it as a C Array in a file called `rom.h`. Three ROMs are provided here:
 
 1. **OSI Basic ROM** (rom.h.OSI)
 - Uses a 6850.
@@ -38,11 +38,24 @@ If you emulate a ROM, provide it as a C Array in a file called `rom.h`. Two ROMs
 - ACIADDRESS: 0xA000
 - ROMADDRESS: 0xB000
 
+3. **Java6502** (rom.h)
+   My own ROM using Microsoft Basic 2
+- RAMSIZE(max): 0xC000
+- ACIADDRESS: 0xC100
+- ROMADDRESS: 0xD000
+
 You can replace with your own ROM, using srec_cat to generate the C Array. See my [ROM Software repo](https://github.com/olivierjan/ROM-software-for-6502-SBC) for more details. 
 
 The code is very basic but is meant to help debug a hombrew computer. It can be greatly optimised and I will try to add new features over time (usable debugging, support for VIAs and other components, etc...).
 
-**WARNING:** Teensy 3.6 is only 3.3v and will provide power to the whole circuit. A 5V version should be possible using Teensy 3.5 but I haven't tested yet. 
+**WARNING:** Teensy 3.6 is only 3.3v and will provide power to the whole circuit. A 5V version should be possible using Teensy 3.5 but I can't get this to work on Teensy 3.5 at the moment. 
+
+### PCB Board
+A PCB to host the Teensy and the 65C02 is provided, I designed it using EasyEDA and ordered it from JLCPCB.
+I provided the design here in Altium and Gerber format, but haven't tested these, only the EasyEDA.
+
+The PCB can be plugged in an existing circuit, and you can choose to power the circuit from Teensy or not using the jumper.
+
 
 Any comments welcome !
 

SBC.h

@@ -1,15 +1,29 @@
-/*
-Bus Access system
-Access 65C02 address and databus on 24 Teensy Pins
-Start simulate some memory for 65c02 to Read/Write.
-*/
+//
+// TEENSY 65C02 
+// 
+// Access 65C02 address and databus using Teensy 3.6(3.3v) or 3.5 (5v)
+// Can simulate RAM, ROM and ACIA (6551 or 6850)
+// Provide access to all pins. 
 
 
-//#define DEBUG
-#define ACIA6551            // Model of ACIA to emulate
+
+//#define DEBUG 0
+#define ACIA6551 1            // Model of ACIA to emulate
+
 //#define ACIA6850          // 6850 or 6551
-#define ROMEMU              // Do we emulate RAM or is it a real chip ? 
+//#define ROMEMU              // Do we emulate RAM or is it a real chip ? 
 //#define RAMEMU              // Do we emulate ROM or is it a real chip ?
+#define BARECPU 1            // Are we just using the 65C02 ? 
+
+#ifdef BARECPU
+    #ifndef ROMEMU  
+        #define ROMEMU 1
+    #endif
+    #ifndef RAMEMU
+        #define RAMEMU 1
+    #endif
+#endif
+
 
 // For the time being, memory map is :
 // 0x0000 - (RAMSIZE-1):                RAM
@@ -18,9 +32,9 @@ Start simulate some memory for 65c02 to Read/Write.
 // Make sure you provide right values below, even if the component is not emulated
 
 
-#define RAMSIZE     0xA000  // Size of RAM to emulate
-#define ACIADDRESS  0xA000  // Base address of Serial Device
-#define ROMADDRESS  0xB000  // Base address of ROM Data 
+#define RAMSIZE     0xC000  // Size of RAM to emulate
+#define ACIADDRESS  0xC100  // Base address of Serial Device
+#define ROMADDRESS  0xD000  // Base address of ROM Data 
                             // make sure your ROM fit as there is nocheck.
                             // if the ROM is too big some of it won't be reachable with 16bits addresses
 
@@ -42,13 +56,23 @@ Start simulate some memory for 65c02 to Read/Write.
 #define ACIASTATUS  ACIADDRESS
 #endif
 
-#define WAITCYCLE   5       // How long do we wante Phase 1 to be.
+#define WAITCYCLE   1       // How long do we wante Phase 1 to be.
 
 // PIN definitions
 
-#define RWPIN       3       // Read/Write' signal
-#define CLOCKPIN    4       // Clock generation
-#define RESETPIN    33      // Reset signal
+#define RWPIN      3       // Read/Write' signal
+#define CLOCKPIN   4       // Clock generation
+#define RESETPIN   33      // Reset signal
+#define BEPIN      24
+#define RDYPIN     34
+#define IRQPIN     27
+#define NMIPIN     26
+#define MLPIN      31
+#define SYNCPIN    32
+#define VPPIN      36
+#define SOPIN      35
+
+// #define SOPIN   
 
 #define GPIOOUTPUT  0xFF       // Value to configure Pins for Output
 #define GPIOINPUT   0x00        // Value to configure Pins for Input