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Correct FormSuffixs, check for indirection.

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Thomas Harte committed 2026-03-13 17:55:47 -04:00
1 parent ae353fb366
commit cfb77d26ce
1 file changed
+22 -19
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Processors/6809/Registers.hpp
+22 -19
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@@ -205,23 +205,23 @@ struct IndexedAddressDecoder {
IndexedAddressDecoder(const uint8_t format) : format_(format) {}
enum FormSuffix: uint8_t {
Offset8bit = 0b00110,
Offset8bitFromPC = 0b01100,
Offset16bit = 0b01001,
Offset16bitFromPC = 0b01101,
NoOffset = 0b00100,
ARegisterOffset = 0b00110,
BRegisterOffset = 0b00101,
DRegisterOffset = 0b01011,
IncrementBy1 = 0b01011,
IncrementBy2 = 0b00001,
DecrementBy1 = 0b00010,
DecrementBy2 = 0b00011,
Offset8bit = 0b1000,
Offset8bitFromPC = 0b1100,
Offset16bit = 0b1001,
Offset16bitFromPC = 0b1101,
NoOffset = 0b0100,
ARegisterOffset = 0b0110,
BRegisterOffset = 0b0101,
DRegisterOffset = 0b1011,
IncrementBy1 = 0b1011,
IncrementBy2 = 0b0001,
DecrementBy1 = 0b0010,
DecrementBy2 = 0b0011,
};
int required_continuation() const {
if(!(format_ & 0x80)) return 0;
switch(format_ & 0b11111) {
switch(format_ & 0b1111) {
using enum FormSuffix;
case Offset8bit: case Offset8bitFromPC: return 1;
case Offset16bit: case Offset16bitFromPC: return 2;
@@ -242,15 +242,15 @@ struct IndexedAddressDecoder {
if(
(format_ & 0x80) &&
(
((format_ & 0b11111) == FormSuffix::Offset8bitFromPC) ||
((format_ & 0b11111) == FormSuffix::Offset16bitFromPC)
((format_ & 0b1111) == FormSuffix::Offset8bitFromPC) ||
((format_ & 0b1111) == FormSuffix::Offset16bitFromPC)
)
) {
return registers.reg<R16::PC>();
}
const int offset = [&] {
switch(format_ & 0b11111) {
switch(format_ & 0b1111) {
default: return 0;
case DecrementBy2: return -2;
case DecrementBy1: return -1;
@@ -275,7 +275,7 @@ struct IndexedAddressDecoder {
return uint16_t(base + (int8_t(format_ << 3) >> 3));
}
switch(format_ & 0b11111) {
switch(format_ & 0b1111) {
using enum FormSuffix;
default: return base;
@@ -285,8 +285,7 @@ struct IndexedAddressDecoder {
case Offset8bitFromPC: return uint16_t(registers.reg<R16::PC>() + int8_t(continuation_));
case Offset16bitFromPC: return uint16_t(registers.reg<R16::PC>() + continuation_);
// TODO: verify that these are signed.
// case ARegisterOffset: return uint16_t(base + int8_t(registers.reg<R8::A>())); // TODO: enable once enum is disambiguated.
case ARegisterOffset: return uint16_t(base + int8_t(registers.reg<R8::A>()));
case BRegisterOffset: return uint16_t(base + int8_t(registers.reg<R8::B>()));
case DRegisterOffset: return base + registers.reg<R16::D>();
}
@@ -294,6 +293,10 @@ struct IndexedAddressDecoder {
return base;
}
bool indirect() const {
return (format_ & 0x90) == 0x90;
}
private:
uint8_t format_;
uint16_t continuation_ = 0;