emul/hw/rc2014: add sdc emulator (wip)

so far, it goes through initialization with the rc2014/sdcard recipe.

emul/hw/rc2014/Makefile

@@ -1,5 +1,5 @@
 EXTOBJS = ../../emul.o ../../libz80/libz80.o
-OBJS = acia.o classic.o 
+OBJS = acia.o sdc.o classic.o 
 TARGET = classic
 
 .PHONY: all

emul/hw/rc2014/classic.c

@@ -13,13 +13,18 @@
 #include <termios.h>
 #include "../../emul.h"
 #include "acia.h"
+#include "sdc.h"
 
 #define RAMSTART 0x8000
 #define ACIA_CTL_PORT 0x80
 #define ACIA_DATA_PORT 0x81
+#define SDC_CSHIGH 0x06
+#define SDC_CSLOW 0x05
+#define SDC_SPI 0x04
 #define MAX_ROMSIZE 0x2000
 
 static ACIA acia;
+static SDC sdc;
 
 static uint8_t iord_acia_ctl()
 {
@@ -41,6 +46,26 @@ static void iowr_acia_data(uint8_t val)
     acia_data_wr(&acia, val);
 }
 
+static uint8_t iord_sdc_spi()
+{
+    return sdc_spi_rd(&sdc);
+}
+
+static void iowr_sdc_spi(uint8_t val)
+{
+    sdc_spi_wr(&sdc, val);
+}
+
+static void iowr_sdc_cshigh(uint8_t val)
+{
+    sdc_cshigh(&sdc);
+}
+
+static void iowr_sdc_cslow(uint8_t val)
+{
+    sdc_cslow(&sdc);
+}
+
 int main(int argc, char *argv[])
 {
     if (argc != 2) {
@@ -81,10 +106,15 @@ int main(int argc, char *argv[])
     }
 
     acia_init(&acia);
+    sdc_init(&sdc);
     m->iord[ACIA_CTL_PORT] = iord_acia_ctl;
     m->iord[ACIA_DATA_PORT] = iord_acia_data;
     m->iowr[ACIA_CTL_PORT] = iowr_acia_ctl;
     m->iowr[ACIA_DATA_PORT] = iowr_acia_data;
+    m->iord[SDC_SPI] = iord_sdc_spi;
+    m->iowr[SDC_SPI] = iowr_sdc_spi;
+    m->iowr[SDC_CSHIGH] = iowr_sdc_cshigh;
+    m->iowr[SDC_CSLOW] = iowr_sdc_cslow;
 
     char tosend = 0;
     while (emul_step()) {

emul/hw/rc2014/sdc.c

@@ -0,0 +1,114 @@
+#include <stdio.h>
+#include "sdc.h"
+
+void sdc_init(SDC *sdc)
+{
+    sdc->selected = false;
+    sdc->initstat = 0;
+    sdc->recvidx = 0;
+    sdc->sendidx = -1;
+    sdc->resp = 0xff;
+}
+
+void sdc_cslow(SDC *sdc)
+{
+    sdc->selected = true;
+}
+
+void sdc_cshigh(SDC *sdc)
+{
+    sdc->selected = false;
+}
+
+void sdc_spi_wr(SDC *sdc, uint8_t val)
+{
+    if (!sdc->selected) {
+        return;
+    }
+    sdc->resp = 0xff;
+    if (sdc->initstat < 8) {
+        // not woken yet.
+        sdc->initstat++;
+        return;
+    }
+    if (sdc->sendidx >= 0) {
+        sdc->resp = sdc->sendbuf[sdc->sendidx++];
+        if (sdc->sendidx == 5) {
+            sdc->sendidx = -1;
+        }
+        return;
+    }
+    if ((sdc->recvidx == 0) && ((val > 0x7f) || (val < 0x40))) {
+        // not a command
+        return;
+    }
+    sdc->recvbuf[sdc->recvidx++] = val;
+    if (sdc->recvidx < 6) {
+        // incomplete command
+        return;
+    }
+    // Command complete
+    val &= 0x3f;
+    sdc->recvidx = 0;
+    uint8_t *b = sdc->recvbuf;
+    fprintf(stderr, "cmd %02x %02x %02x %02x %02x\n", b[0], b[1], b[2], b[3], b[4]);
+    uint8_t cmd = b[0] & 0x3f;
+    if (sdc->initstat == 8) {
+        // At this stage, we're expecting CMD0
+        if (cmd == 0) {
+            sdc->initstat++;
+            sdc->sendbuf[4] = 0x01;
+            sdc->sendidx = 4;
+        }
+        return;
+    }
+    if (sdc->initstat == 9) {
+        // At this stage, we're expecting CMD8 with 0x1aa arg2
+        if ((cmd == 8) && (b[3] == 0x01) && (b[4] == 0xaa)) {
+            sdc->initstat++;
+            sdc->sendbuf[0] = 0x01;
+            sdc->sendbuf[1] = 0;
+            sdc->sendbuf[2] = 0;
+            sdc->sendbuf[3] = 0x01;
+            sdc->sendbuf[4] = 0xaa;
+            sdc->sendidx = 0;
+        } else {
+            sdc-> initstat = 8;
+        }
+        return;
+    }
+    if (sdc->initstat == 10) {
+        // At this stage, we're expecting CMD55
+        if (cmd == 55) {
+            sdc->initstat++;
+            sdc->sendbuf[4] = 0x01;
+            sdc->sendidx = 4;
+        } else {
+            sdc->initstat = 8;
+        }
+        return;
+    }
+    if (sdc->initstat == 11) {
+        // At this stage, we're expecting CMD41
+        if ((cmd == 41) && (b[1] == 0x40) && (b[2] == 0x00)) {
+            sdc->initstat++;
+            sdc->sendbuf[4] = 0x00;
+            sdc->sendidx = 4;
+        } else {
+            sdc->initstat = 8;
+        }
+        return;
+    }
+    // We have a fully initialized card.
+    // Simulate success for any unknown command.
+    sdc->sendbuf[4] = 0x00;
+    sdc->sendidx = 4;
+}
+
+uint8_t sdc_spi_rd(SDC *sdc)
+{
+    if (!sdc->selected) {
+        return 0xff;
+    }
+    return sdc->resp;
+}

emul/hw/rc2014/sdc.h

@@ -0,0 +1,28 @@
+#include <stdint.h>
+#include <stdbool.h>
+
+typedef struct {
+    bool selected;
+    // Initialization status. 0 == not woken 8 == woken 9 == CMD0 received
+    // 10 == CMD8 received, 11 == CMD55 received, 12 == CMD41 received (fully
+    // initialized).
+    unsigned int initstat;
+    // We receive commands into this buffer.
+    uint8_t recvbuf[6];
+    // Where the next SPI byte should be stored in recvbuf.
+    unsigned int recvidx;
+    // Buffer to the arguments for a response
+    uint8_t sendbuf[5];
+    // Index of the next byte from sendbuf we should return. If -1, buffer is
+    // empty.
+    int sendidx;
+    // One byte response. When all other response buffers are empty, return
+    // this.
+    uint8_t resp;
+} SDC;
+
+void sdc_init(SDC *sdc);
+void sdc_cslow(SDC *sdc);
+void sdc_cshigh(SDC *sdc);
+void sdc_spi_wr(SDC *sdc, uint8_t val);
+uint8_t sdc_spi_rd(SDC *sdc);