emul/z80: decouple SDC and SPI

My idea of plugging a RC2014 bridge directly onto a Sega Master System
cartridge doesn't work. The SMS eats all I/O addr space, we can't use
it. Therefore, this naive idea, in the emulator, of reusing sdc.c in
sms.c as-is, doesn't work either.

I'll have to find another way of communicating to a SPI device on the
SMS. I'll probably do it through a controller port. Meanwhile, I need
to decouple SPI from SDC in the emulator code so that I can reuse
sdc.c. This is what is done here.

emul/z80/Makefile

@@ -1,6 +1,6 @@
 TARGETS = forth rc2014 sms ti84
 OBJS = emul.o z80.o
-RC2014_OBJS = $(OBJS) sio.o acia.o sdc.o
+RC2014_OBJS = $(OBJS) sio.o acia.o sdc.o rc2014_spi.o
 SMS_OBJS = $(OBJS) sms_vdp.o sms_ports.o sms_pad.o ps2_kbd.o sdc.o
 TI84_OBJS = $(OBJS) t6a04.o ti84_kbd.o 
 CDIR = ../../cvm

emul/z80/emul.h

@@ -5,6 +5,7 @@
 
 typedef byte (*IORD) ();
 typedef void (*IOWR) (byte data);
+typedef byte (*EXCH) (byte data);
 
 typedef struct {
     Z80Context cpu;

emul/z80/rc2014.c

@@ -15,6 +15,7 @@
 #include "acia.h"
 #include "sio.h"
 #include "sdc.h"
+#include "rc2014_spi.h"
 
 #define RAMSTART 0x8000
 #define ACIA_CTL_PORT 0x80
@@ -29,6 +30,7 @@ bool use_sio = false;
 static ACIA acia;
 static SIO sio;
 static SDC sdc;
+static SPI spi;
 
 static uint8_t iord_acia_ctl()
 {
@@ -70,26 +72,28 @@ static void iowr_sio_data(uint8_t val)
     sio_adata_wr(&sio, val);
 }
 
-static uint8_t iord_sdc_spi()
+static uint8_t iord_spi()
 {
-    return sdc_spi_rd(&sdc);
+    return spi_rd(&spi);
 }
 
-static void iowr_sdc_spi(uint8_t val)
+static void iowr_spi(uint8_t val)
 {
-    sdc_spi_wr(&sdc, val);
+    spi_wr(&spi, val);
 }
 
+byte spix_sdc(byte val) { return sdc_spix(&sdc, val); }
+
 // in emulation, exchanges are always instantaneous, so we
 // always report as ready.
-static uint8_t iord_sdc_ctl()
+static uint8_t iord_spi_ctl()
 {
     return 0;
 }
 
-static void iowr_sdc_ctl(uint8_t val)
+static void iowr_spi_ctl(uint8_t val)
 {
-    sdc_ctl_wr(&sdc, val);
+    spi_ctl_wr(&spi, val);
 }
 
 static bool has_irq()
@@ -134,6 +138,7 @@ int main(int argc, char *argv[])
     acia_init(&acia);
     sio_init(&sio);
     sdc_init(&sdc);
+    spi_init(&spi, spix_sdc);
 
     while ((ch = getopt(argc, argv, "sc:")) != -1) {
         switch (ch) {
@@ -198,10 +203,10 @@ int main(int argc, char *argv[])
         m->iowr[ACIA_CTL_PORT] = iowr_acia_ctl;
         m->iowr[ACIA_DATA_PORT] = iowr_acia_data;
     }
-    m->iord[SDC_SPI] = iord_sdc_spi;
+    m->iord[SDC_SPI] = iord_spi;
-    m->iowr[SDC_SPI] = iowr_sdc_spi;
+    m->iowr[SDC_SPI] = iowr_spi;
-    m->iord[SDC_CTL] = iord_sdc_ctl;
+    m->iord[SDC_CTL] = iord_spi_ctl;
-    m->iowr[SDC_CTL] = iowr_sdc_ctl;
+    m->iowr[SDC_CTL] = iowr_spi_ctl;
 
     char tosend = 0;
     while (emul_step()) {

emul/z80/rc2014_spi.c

@@ -0,0 +1,28 @@
+#include "rc2014_spi.h"
+
+void spi_init(SPI *spi, EXCH spixfn)
+{
+    spi->selected = false;
+    spi->resp = 0xff;
+    spi->spixfn = spixfn;
+}
+
+// TODO: for now, any nonzero value enables the SPI. To allow
+// emulation of systems with multi-devices SPI relay, change
+// this.
+void spi_ctl_wr(SPI *spi, byte val)
+{
+    spi->selected = val;
+}
+
+void spi_wr(SPI *spi, byte val)
+{
+    if (spi->selected) {
+        spi->resp = spi->spixfn(val);
+    }
+}
+
+byte spi_rd(SPI *spi)
+{
+    return spi->selected ? spi->resp : 0xff;
+}

emul/z80/rc2014_spi.h

@@ -0,0 +1,17 @@
+#include "emul.h"
+
+/* Emulates a SPI relay designed for the RC2014, enabled by poking on the CTL
+   port, then allowing a SPI exchange by writing to, then reading from, the
+   data port.
+*/
+
+typedef struct {
+    bool selected;
+    byte resp;
+    EXCH spixfn;
+} SPI;
+    
+void spi_init(SPI *spi, EXCH spixfn);
+void spi_ctl_wr(SPI *spi, byte val);
+void spi_wr(SPI *spi, byte val);
+byte spi_rd(SPI *spi);

emul/z80/sdc.c

@@ -13,47 +13,34 @@ static uint16_t crc16(uint16_t crc, uint8_t data)
 
 void sdc_init(SDC *sdc)
 {
-    sdc->selected = false;
     sdc->initstat = 0;
     sdc->recvidx = 0;
     sdc->sendidx = -1;
-    sdc->resp = 0xff;
     sdc->fp = NULL;
     sdc->cmd17bytes = -1;
     sdc->cmd24bytes = -2;
 }
 
-// TODO: for now, any nonzero value enables the SDC. To allow
+byte sdc_spix(SDC *sdc, byte val)
-// emulation of systems with multi-devices SPI relay, change
-// this.
-void sdc_ctl_wr(SDC *sdc, uint8_t val)
 {
-    sdc->selected = val;
+    byte resp = 0xff;
-}
-
-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;
+        return resp;
     }
     if (sdc->sendidx >= 0) {
-        sdc->resp = sdc->sendbuf[sdc->sendidx++];
+        resp = sdc->sendbuf[sdc->sendidx++];
         if (sdc->sendidx == 5) {
             sdc->sendidx = -1;
         }
-        return;
+        return resp;
     }
     if (sdc->cmd17bytes >= 0) {
         if (sdc->fp) {
-            sdc->resp = getc(sdc->fp);
+            resp = getc(sdc->fp);
         }
-        sdc->crc16 = crc16(sdc->crc16, sdc->resp);
+        sdc->crc16 = crc16(sdc->crc16, resp);
         sdc->cmd17bytes++;
         if (sdc->cmd17bytes == 512) {
             sdc->sendbuf[3] = sdc->crc16 >> 8;
@@ -61,12 +48,12 @@ void sdc_spi_wr(SDC *sdc, uint8_t val)
             sdc->sendidx = 3;
             sdc->cmd17bytes = -1;
         }
-        return;
+        return resp;
     }
     if (sdc->cmd24bytes == -1) {
         if (val == 0xff) {
             // it's ok to receive idle bytes before the data token.
-            return;
+            return resp;
         }
         if (val == 0xfe) {
             // data token, good
@@ -75,7 +62,7 @@ void sdc_spi_wr(SDC *sdc, uint8_t val)
             // something is wrong, cancel cmd24
             sdc->cmd24bytes = -2;
         }
-        return;
+        return resp;
     }
     if (sdc->cmd24bytes >= 0) {
         if (sdc->cmd24bytes < 512) {
@@ -102,16 +89,16 @@ void sdc_spi_wr(SDC *sdc, uint8_t val)
             sdc->cmd24bytes = -3;
         }
         sdc->cmd24bytes++;
-        return;
+        return resp;
     }
     if ((sdc->recvidx == 0) && ((val > 0x7f) || (val < 0x40))) {
         // not a command
-        return;
+        return resp;
     }
     sdc->recvbuf[sdc->recvidx++] = val;
     if (sdc->recvidx < 6) {
         // incomplete command
-        return;
+        return resp;
     }
     // Command complete
     val &= 0x3f;
@@ -128,7 +115,7 @@ void sdc_spi_wr(SDC *sdc, uint8_t val)
             sdc->sendbuf[4] = 0x01;
             sdc->sendidx = 4;
         }
-        return;
+        return resp;
     }
     if (sdc->initstat == 9) {
         // At this stage, we're expecting CMD8 with 0x1aa arg2
@@ -143,7 +130,7 @@ void sdc_spi_wr(SDC *sdc, uint8_t val)
         } else {
             sdc-> initstat = 8;
         }
-        return;
+        return resp;
     }
     if (sdc->initstat == 10) {
         // At this stage, we're expecting CMD55
@@ -154,7 +141,7 @@ void sdc_spi_wr(SDC *sdc, uint8_t val)
         } else {
             sdc->initstat = 8;
         }
-        return;
+        return resp;
     }
     if (sdc->initstat == 11) {
         // At this stage, we're expecting CMD41
@@ -165,7 +152,7 @@ void sdc_spi_wr(SDC *sdc, uint8_t val)
         } else {
             sdc->initstat = 8;
         }
-        return;
+        return resp;
     }
     // We have a fully initialized card.
     if (cmd == 17) {
@@ -178,7 +165,7 @@ void sdc_spi_wr(SDC *sdc, uint8_t val)
         sdc->sendidx = 3;
         sdc->cmd17bytes = 0;
         sdc->crc16 = 0;
-        return;
+        return resp;
     }
     if (cmd == 24) {
         if (sdc->fp) {
@@ -188,17 +175,10 @@ void sdc_spi_wr(SDC *sdc, uint8_t val)
         sdc->sendidx = 4;
         sdc->cmd24bytes = -1;
         sdc->crc16 = 0;
-        return;
+        return resp;
     }
     // Simulate success for any unknown command.
     sdc->sendbuf[4] = 0x00;
     sdc->sendidx = 4;
-}
+    return resp;
-
-uint8_t sdc_spi_rd(SDC *sdc)
-{
-    if (!sdc->selected) {
-        return 0xff;
-    }
-    return sdc->resp;
 }

emul/z80/sdc.h

@@ -1,24 +1,19 @@
-#include <stdint.h>
+#include "emul.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];
+    byte 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];
+    byte 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;
     // File used for contents read/write
     FILE *fp;
     // number of bytes read into the current CMD17. -1 means no CMD17 active.
@@ -31,6 +26,4 @@ typedef struct {
 } SDC;
 
 void sdc_init(SDC *sdc);
-void sdc_ctl_wr(SDC *sdc, uint8_t val);
+byte sdc_spix(SDC *sdc, byte val);
-void sdc_spi_wr(SDC *sdc, uint8_t val);
-uint8_t sdc_spi_rd(SDC *sdc);

emul/z80/sms.c

@@ -90,7 +90,8 @@ static void iowr_ports_ctl(uint8_t val)
     ports_ctl_wr(&ports, val);
 }
 
-static uint8_t iord_sdc_spi()
+// TODO: re-add as controller-based SPI
+/* static uint8_t iord_sdc_spi()
 {
     return sdc_spi_rd(&sdc);
 }
@@ -110,7 +111,7 @@ static uint8_t iord_sdc_ctl()
 static void iowr_sdc_ctl(uint8_t val)
 {
     sdc_ctl_wr(&sdc, val);
-}
+}*/
 
 void create_window()
 {
@@ -356,10 +357,12 @@ int main(int argc, char *argv[])
     m->iowr[VDP_CMD_PORT] = iowr_vdp_cmd;
     m->iowr[VDP_DATA_PORT] = iowr_vdp_data;
     m->iowr[PORTS_CTL_PORT] = iowr_ports_ctl;
+    /* TODO: re-add
     m->iord[SDC_SPI] = iord_sdc_spi;
     m->iowr[SDC_SPI] = iowr_sdc_spi;
     m->iord[SDC_CTL] = iord_sdc_ctl;
     m->iowr[SDC_CTL] = iowr_sdc_ctl;
+    */
 
     conn = xcb_connect(NULL, NULL);
     screen = xcb_setup_roots_iterator(xcb_get_setup(conn)).data;

recipes/rc2014/blk/619

@@ -1,13 +1,15 @@
 0xff00 CONSTANT RS_ADDR        0xfffa CONSTANT PS_ADDR
 RS_ADDR 0x80 - CONSTANT SYSVARS
 0x8000 CONSTANT HERESTART
+4 CONSTANT SPI_DATA 5 CONSTANT SPI_CTL 1 CONSTANT SDC_DEVID
 602 LOAD  ( acia decl )
 5 LOAD    ( z80 assembler )
 262 LOAD  ( xcomp )            282 LOAD  ( boot.z80.decl )
 270 LOAD  ( xcomp overrides )  283 335 LOADR ( boot.z80 )
 353 LOAD  ( xcomp core low )   603 605 LOADR ( acia )
+419 LOAD 423 436 LOADR
 390 LOAD  ( xcomp core high )
 (entry) _
 ( Update LATEST )
 PC ORG @ 8 + !
-," ACIA$ " EOT,
+," ACIA$ BLK$ " EOT,