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It seems a full CRC is in play.

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This commit is contained in:
Thomas Harte 2021-03-12 22:45:48 -05:00
parent a32a2f36be
commit 7a8317ad81
1 changed files with 21 additions and 1 deletions
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22
Machines/AmstradCPC/AmstradCPC.cpp
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@ -32,6 +32,8 @@
#include "../../Analyser/Static/AmstradCPC/Target.hpp"
#include "../../Numeric/CRC.hpp"
#include <array>
#include <cstdint>
#include <vector>
@ -934,6 +936,22 @@ template <bool has_fdc> class ConcreteMachine:
// In A ROM-esque fashion, begin the first pulse after the final one
// that was just consumed.
tape_player_.complete_pulse();
// Update in-memory CRC.
auto crc_value =
uint16_t(
read_pointers_[tape_crc_address >> 14][tape_crc_address & 16383] |
(read_pointers_[(tape_crc_address+1) >> 14][(tape_crc_address+1) & 16383] << 8)
);
tape_crc_.set_value(crc_value);
tape_crc_.add(*byte);
crc_value = tape_crc_.get_value();
write_pointers_[tape_crc_address >> 14][tape_crc_address & 16383] = uint8_t(crc_value);
write_pointers_[(tape_crc_address+1) >> 14][(tape_crc_address+1) & 16383] = uint8_t(crc_value >> 8);
// Indicate successful byte read.
z80_.set_value_of_register(CPU::Z80::Register::A, *byte);
flags |= CPU::Z80::Flag::Carry;
} else {
@ -1241,6 +1259,8 @@ template <bool has_fdc> class ConcreteMachine:
// therefore the has_fdc template flag is sufficient to locate them.
static constexpr uint16_t tape_read_byte_address = has_fdc ? 0x2b20 : 0x29b0;
static constexpr uint16_t tape_speed_value_address = has_fdc ? 0xb1e7 : 0xbc8f;
static constexpr uint16_t tape_crc_address = has_fdc ? 0xb1eb : 0xb8d3;
CRC::CCITT tape_crc_;
HalfCycles clock_offset_;
HalfCycles crtc_counter_;
@ -1258,7 +1278,7 @@ template <bool has_fdc> class ConcreteMachine:
ROMType upper_rom_;
uint8_t *ram_pages_[4];
uint8_t *read_pointers_[4];
const uint8_t *read_pointers_[4];
uint8_t *write_pointers_[4];
KeyboardState key_state_;