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minimacplus/components/tme/scc.c

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#include <stdio.h>
#include <stdint.h>
#include "scc.h"
#include "m68k.h"
#include "hexdump.h"
#include "localtalk.h"
/*
Emulation of the Zilog 8530 SCC.
This is an extremely minimal SCC implementation: it only somewhat implements the interrupt mechanism for the
DCD pins because that is what is needed for the mouse to work.
*/
void sccIrq(int ena);
#define BUFLEN 8192
typedef struct {
int dcd;
int cts;
int wr1;
int sdlcaddr;
int wr15;
int hunting;
int txTimer;
uint8_t txData[BUFLEN];
uint8_t rxData[BUFLEN];
int txPos, rxPos, rxLen;
int rxDelay;
} SccChan;
typedef struct {
int regptr;
int intpending;
int intpendingOld;
SccChan chan[2];
} Scc;
static Scc scc;
//WR15 is the External/Status Interrupt Control and has the interrupt enable bits.
#define SCC_WR15_BREAK (1<<7)
#define SCC_WR15_TXU (1<<6)
#define SCC_WR15_CTS (1<<5)
#define SCC_WR15_SYNC (1<<4)
#define SCC_WR15_DCD (1<<3)
#define SCC_WR15_ZCOUNT (1<<1)
//WR3, when read, gives the Interrupt Pending status.
//This is reflected in scc.intpending.
#define SCC_WR3_CHB_EXT (1<<0)
#define SCC_WR3_CHB_TX (1<<1)
#define SCC_WR3_CHB_RX (1<<2)
#define SCC_WR3_CHA_EXT (1<<3)
#define SCC_WR3_CHA_TX (1<<4)
#define SCC_WR3_CHA_RX (1<<5)
static void raiseInt(int chan) {
if ((scc.chan[chan].wr1&1) && (scc.intpending&(~scc.intpendingOld))) {
scc.intpendingOld=scc.intpending;
// printf("SCC int, pending %x\n", scc.intpending);
sccIrq(1);
}
}
void sccSetDcd(int chan, int val) {
val=val?1:0;
if (scc.chan[chan].dcd!=val) {
if (chan==SCC_CHANA) {
if (scc.chan[SCC_CHANA].wr15&SCC_WR15_DCD) {
scc.intpending|=SCC_WR3_CHA_EXT;
raiseInt(SCC_CHANA);
}
} else {
if (scc.chan[SCC_CHANB].wr15&SCC_WR15_DCD) {
scc.intpending|=SCC_WR3_CHB_EXT;
raiseInt(SCC_CHANB);
}
}
}
scc.chan[chan].dcd=val;
}
void sccTxFinished(int chan) {
hexdump(scc.chan[chan].txData, scc.chan[chan].txPos);
localtalkSend(scc.chan[chan].txData, scc.chan[chan].txPos);
scc.chan[chan].txPos=0;
scc.chan[chan].hunting=1;
}
void sccRecv(int chan, uint8_t *data, int len) {
memcpy(scc.chan[chan].rxData, data, len);
scc.chan[chan].rxData[len]=0xA5; //crc1
scc.chan[chan].rxData[len+1]=0xA5; //crc2
scc.chan[chan].rxData[len+2]=0; //abort
scc.chan[chan].rxLen=len+3;
scc.chan[chan].rxDelay=30;
}
static void triggerRx(int chan) {
if (!scc.chan[chan].hunting) return;
printf("Receiving:\n");
hexdump(scc.chan[chan].rxData, scc.chan[chan].rxLen);
if (scc.chan[chan].rxData[0]==0xFF || scc.chan[chan].rxData[0]==scc.chan[chan].sdlcaddr) {
scc.chan[chan].rxPos=0;
//Sync int
if (scc.chan[chan].wr15&SCC_WR15_SYNC) {
scc.intpending|=(chan?SCC_WR3_CHA_EXT:SCC_WR3_CHB_EXT);
raiseInt(chan);
}
//RxD int
int rxintena=scc.chan[chan].wr1&0x18;
if (rxintena==0x10 || rxintena==0x08) {
scc.intpending|=(chan?SCC_WR3_CHA_RX:SCC_WR3_CHB_RX);
raiseInt(chan);
}
scc.chan[chan].hunting=0;
} else {
scc.chan[chan].rxLen=0;
}
}
void sccWrite(unsigned int addr, unsigned int val) {
int chan, reg;
if (addr & (1<<1)) chan=SCC_CHANA; else chan=SCC_CHANB;
if (addr & (1<<2)) {
//Data
reg=8;
} else {
//Control
reg=scc.regptr;
scc.regptr=0;
}
if (reg==0) {
scc.regptr=val&0x7;
if ((val&0x38)==0x8) scc.regptr|=8;
if ((val&0x38)==0x10) {
scc.intpending=0;
scc.intpendingOld=0;
}
if ((val&0x38)==0x18) {
//SCC abort: parse whatever we sent
printf("SCC ABORT: Sent data\n");
sccTxFinished(chan);
}
if ((val&0xc0)==0xC0) {
//reset tx underrun latch
if (scc.chan[chan].txTimer==0) scc.chan[chan].txTimer=-1;
}
} else if (reg==1) {
scc.chan[chan].wr1=val;
} else if (reg==3) {
//bitsperchar1, bitsperchar0, autoenables, enterhuntmode, rxcrcen, addresssearch, synccharloadinh, rxena
//autoenable: cts = tx ena, dcd = rx ena
if (val&0x10) scc.chan[chan].hunting=1;
} else if (reg==6) {
scc.chan[chan].sdlcaddr=val;
} else if (reg==8) {
scc.chan[chan].txData[scc.chan[chan].txPos++]=val;
printf("TX! Pos %d\n", scc.chan[chan].txPos);
scc.chan[chan].txTimer+=30;
} else if (reg==15) {
scc.chan[chan].wr15=val;
}
// printf("SCC: write to addr %x chan %d reg %d val %x\n", addr, chan, reg, val);
}
unsigned int sccRead(unsigned int addr) {
int chan, reg, val=0xff;
if (addr & (1<<1)) chan=SCC_CHANA; else chan=SCC_CHANB;
if (addr & (1<<2)) {
//Data
reg=8;
} else {
//Control
reg=scc.regptr;
scc.regptr=0;
}
if (reg==0) {
val=(1<<2); //tx buffer always empty
if (scc.chan[chan].rxLen && !scc.chan[chan].rxDelay) val|=(1<<0);
if (scc.chan[chan].txTimer==0) val|=(1<<6);
if (scc.chan[chan].dcd) val|=(1<<3);
if (scc.chan[chan].cts) val|=(1<<5);
if (scc.chan[chan].hunting) val|=(1<<4);
if (scc.chan[chan].rxPos==scc.chan[chan].rxLen-1) val|=(1<<7); //abort
} else if (reg==1) {
//EndOfFrame, CRCErr, RXOverrun, ParityErr, Residue0, Residue1, Residue2, AllSent
val=0x7; //residue code 011, all sent
if (scc.chan[chan].rxPos==scc.chan[chan].rxLen-2) val|=(1<<7); //end of frame
} else if (reg==2 && chan==SCC_CHANB) {
//We assume this also does an intack.
int rsn=0;
if (scc.intpending & SCC_WR3_CHB_EXT) {
rsn=1;
scc.intpending&=~SCC_WR3_CHB_EXT;
}
if (scc.intpending & SCC_WR3_CHA_EXT) {
rsn=5;
scc.intpending&=~SCC_WR3_CHA_EXT;
}
val=rsn<<1;
if (scc.intpending&0x38) raiseInt(SCC_CHANA);
if (scc.intpending&0x07) raiseInt(SCC_CHANB);
} else if (reg==3) {
if (chan==SCC_CHANA) val=scc.intpending; else val=0;
} else if (reg==8) {
//rx buffer
if (scc.chan[chan].rxLen && !scc.chan[chan].rxDelay) {
val=scc.chan[chan].rxData[scc.chan[chan].rxPos++];
if (scc.chan[chan].rxPos==scc.chan[chan].rxLen) {
scc.chan[chan].rxLen=0;
} else {
int rxintena=scc.chan[chan].wr1&0x18;
if (rxintena==0x10) {
scc.intpending|=(chan?SCC_WR3_CHA_RX:SCC_WR3_CHB_RX);
raiseInt(chan);
}
}
if (scc.chan[chan].rxPos==scc.chan[chan].rxLen-1) scc.chan[chan].hunting=1;
if (scc.chan[chan].rxPos==scc.chan[chan].rxLen-1 && scc.chan[chan].wr15&SCC_WR15_BREAK) {
scc.intpending|=(chan?SCC_WR3_CHA_EXT:SCC_WR3_CHB_EXT);
raiseInt(chan);
}
} else {
val=0;
}
} else if (reg==10) {
//Misc status (mostly SDLC)
val=0;
} else if (reg==15) {
val=scc.chan[chan].wr15;
}
// printf("SCC: read from chan %d reg %d val %x\n", chan, reg, val);
return val;
}
//Called at about 800KHz
void sccTick() {
for (int n=0; n<2; n++) {
if (scc.chan[n].txTimer>0) {
scc.chan[n].txTimer--;
if (scc.chan[n].txTimer==0) {
printf("Tx buffer empty: Sent data\n");
sccTxFinished(n);
}
}
if (scc.chan[n].rxDelay!=0) {
scc.chan[n].rxDelay--;
if (scc.chan[n].rxDelay==0) {
triggerRx(n);
}
}
}
}
void sccInit() {
sccSetDcd(1, 1);
sccSetDcd(2, 1);
scc.chan[0].txTimer=-1;
scc.chan[1].txTimer=-1;
}
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