on-chip FRT experiment

main.c

@@ -2,6 +2,7 @@
 #include "vdp1.h"
 #include "scu.h"
 #include "smpc.h"
+#include "sh2.h"
 
 void fill_32(u32 * buf, u32 v, s32 n)
 {
@@ -16,9 +17,13 @@ void timer0_int(void) __attribute__ ((interrupt_handler));
 void timer0_int(void)
 {
   scu.reg.IST &= ~(IST__TIMER0);
+}
 
-  // The SMPC uses the V-BLANK-IN interrupt to execute internal tasks. At this
-  // time, issuing commands for 300 µs from V-BLANK-IN is prohibited.
+void oci_int(void) __attribute__ ((interrupt_handler));
+void oci_int(void)
+{
+  // clear OCFA
+  sh2.reg.FTCSR &= ~(FTCSR__OCFA);
 
   while (smpc.reg.SF != 0) {}
 
@@ -193,10 +198,53 @@ void start(void)
 
   vec[SCU_VEC__TIMER0] = (u32)(&timer0_int);
   vec[SCU_VEC__SMPC] = (u32)(&smpc_int);
-  scu.reg.T0C = 5;
-  scu.reg.T1MD = T1MD__TENB;
+  //scu.reg.T0C = 5;
+  //scu.reg.T1MD = T1MD__TENB;
+
+  // From the SMPC manual:
+  //   The SMPC uses the V-BLANK-IN interrupt to execute internal tasks. At this
+  //   time, issuing commands for 300 µs from V-BLANK-IN is prohibited.
+
+  // CLKCHG320 (power-on default) NTSC, the FRC's internal clock is 26.8741 MHz.
+  // The possible periods are then:
+  //
+  //  - 0.29768 µs (/8)
+  //  - 1.19074 µs (/32)
+  //  - 4.76295 µs (/128)
+  //
+  // (1/(26.8741 MHz)) * 128 * 63 = 300.066 µs
+
+  // FRC, OCRA, OCRB, and FCIR are 16-bit registers, but the FRT bus is an 8-bit
+  // bus.
+
+  // TCR set CKS to /128
+  // TOCR set OCRS to OCRA
+  // TIER set OCIAE
+  // FTCSR set CCLRA (clear FRC on compare match A)
+  // VCRC set FOCV
+  // OCRA set 63
+  // FRC set 0
+
+  vec[0x60] = (u32)&oci_int;
+  sh2.reg.VCRC = VCRC__FOCV(0x60);
+
+  sh2.reg.TCR = TCR__CKS__INTERNAL_DIV128;
+  sh2.reg.TOCR = TOCR__OCRS__OCRA;
+  sh2.reg.FTCSR = FTCSR__CCLRA;
+  sh2.reg.OCRAB.H = 0;   // Even though Kronos doesn't emulate this, SH7095 says
+                        // we are required to write the upper bit prior to
+                        // writing the lower byte
+  sh2.reg.OCRAB.L = 63;
+  sh2.reg.FRC.H = 0;
+  sh2.reg.FRC.L = 0;
+
+  // enable output compare interrupt
+  sh2.reg.TIER = TIER__OCIAE;
+
+  // reset/enable interrupts
+
   scu.reg.IST = 0;
-  scu.reg.IMS = ~(IMS__TIMER0 | IMS__SMPC);
+  scu.reg.IMS = ~(IMS__SMPC);
 
   while (1) {
     vec[0] = scu.reg.IST;

scu.h

@@ -160,5 +160,3 @@ enum scu_vec {
 };
 
 static_assert(SCU_VEC__EXT15 == 0x5f);
-
-extern reg32 vec[0x60] __asm("vec");

sh2.h

@@ -10,11 +10,20 @@ typedef struct sh2_reg {
   reg8 _res0[10];
   reg8 TIER;     // 0x010
   reg8 FTCSR;    // 0x011
-  reg16 FRC;     // 0x012
-  reg16 OCRA_B;  // 0x014
+  struct {
+    reg8 H;      // 0x012
+    reg8 L;      // 0x013
+  } FRC;
+  struct {
+    reg8 H;      // 0x014
+    reg8 L;      // 0x015
+  } OCRAB;
   reg8 TCR;      // 0x016
   reg8 TOCR;     // 0x017
-  reg16 FICR;    // 0x018
+  struct {
+    reg8 H;      // 0x018
+    reg8 L;      // 0x018
+  } FICR;
   reg8 _res1[70];
   reg16 IPRB;    // 0x060
   reg16 VCRA;    // 0x062
@@ -87,7 +96,7 @@ typedef struct sh2_reg {
 } sh2_reg;
 
 static_assert((sizeof (struct sh2_reg)) == 0x200);
-static_assert((offsetof (struct sh2_reg, OCRA_B)) == 0x014);
+static_assert((offsetof (struct sh2_reg, OCRAB)) == 0x014);
 static_assert((offsetof (struct sh2_reg, BCR1)) == 0x1e0);
 
 struct sh2 {
@@ -95,3 +104,47 @@ struct sh2 {
 };
 
 extern struct sh2 sh2 __asm("sh2");
+
+extern reg32 vec[0xff] __asm("vec");
+
+enum tier_bits {
+  TIER__ICIE = (1 << 7),
+  TIER__OCIAE = (1 << 3),
+  TIER__OCIBE = (1 << 2),
+  TIER__OVIE = (1 << 1),
+};
+enum ftcsr_bits {
+  FTCSR__ICF = (1 << 7),
+  FTCSR__OCFA = (1 << 3),
+  FTCSR__OCFB = (1 << 2),
+  FTCSR__OVF = (1 << 1),
+  FTCSR__CCLRA = (1 << 0),
+};
+enum tcr_bits {
+  TCR__IEDGA__RISING_EDGE = (1 << 7),
+  TCR__CKS__INTERNAL_DIV8 = (0b00),
+  TCR__CKS__INTERNAL_DIV32 = (0b01),
+  TCR__CKS__INTERNAL_DIV128 = (0b10),
+  TCR__CKS__EXTERNAL_RISING = (0b11),
+};
+enum tocr_bits {
+  TOCR__OCRS__OCRA = (0 << 4),
+  TOCR__OCRS__OCRB = (1 << 4),
+  TOCR__OLVLA = (1 << 1),
+  TOCR__OLBLB = (1 << 0),
+};
+// enum vcra_bits {
+#define VCRA__SERV(n) (n << 8)
+#define VCRA__SRXV(n) (n << 0)
+// };
+// enum vcrb_bits {
+#define VCRB__STXV(n) (n << 8)
+#define VCRB__STEV(n) (n << 0)
+// };
+// enum vcrc_bits {
+#define VCRC__FICV(n) (n << 8) // input-capture interrupt vector number
+#define VCRC__FOCV(n) (n << 0) // output-compare interrupt vector number
+// };
+// enum vcrd_bits {
+#define VCRD__FOVV(n) (n << 8)
+// };