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sms, improve vdp (sprite collision, hcounter latch)

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This commit is contained in:
kub 2021-10-18 23:05:58 +02:00
parent 646be42e9d
commit cc1547e8cd
2 changed files with 49 additions and 16 deletions
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18
pico/sms.c
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@ -22,6 +22,7 @@ extern void YM2413_dataWrite(unsigned data);
static unsigned short ymflag = 0xffff;
static u8 vdp_buffer;
static u8 vdp_hlatch;
static unsigned char vdp_data_read(void)
{
@ -156,12 +157,8 @@ static unsigned char z80_sms_in(unsigned short a)
elprintf(EL_HVCNT, "V counter read: %02x", d);
break;
case 0x41: /* H counter, TODO: latched by toggle of pad TH line */
// 171 slots per scanline of 228 clocks, runs from 0x85-0x93,0xe9-0x84
#define CYC2SLOT (256 * 171/228) // cycles to slot factor in Q8
d = 228-z80_cyclesLeft;
if (d <= 19) d = (( d * CYC2SLOT)>>8) + 0x85;
else d = (((d-20) * CYC2SLOT)>>8) + 0xe9;
case 0x41: /* H counter */
d = vdp_hlatch;
elprintf(EL_HVCNT, "H counter read: %02x", d);
break;
@ -218,6 +215,15 @@ static void z80_sms_out(unsigned short a, unsigned char d)
switch (a)
{
case 0x01:
// latch hcounter if one of the TH lines is switched to 1
if ((Pico.ms.io_ctl ^ d) & d & 0xa0) {
unsigned c = 228-z80_cyclesLeft;
// 171 slots per scanline of 228 clocks, runs from 0xf4-0x93,0xe9-0xf3
// this matches h counter tables in SMSVDPTest
c = (((c+2) * ((171<<8)/228))>>8)-1 + 0xf4; // Q8 to avoid dividing
if (c > 0x193) c += 0xe9-0x93-1;
vdp_hlatch = (u8)c;
}
Pico.ms.io_ctl = d;
break;