mirror of
https://github.com/davidgiven/fluxengine.git
synced 2025-10-31 11:17:01 -07:00
135 lines
3.0 KiB
C++
135 lines
3.0 KiB
C++
#include "globals.h"
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#include "fluxmap.h"
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#include "decoders/fluxmapreader.h"
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#include "protocol.h"
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#include "record.h"
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#include "decoders/decoders.h"
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#include "sector.h"
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#include "fb100.h"
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#include "crc.h"
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#include "bytes.h"
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#include "decoders/rawbits.h"
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#include "track.h"
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#include "fmt/format.h"
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#include <string.h>
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#include <algorithm>
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const FluxPattern SECTOR_ID_PATTERN(16, 0xabaa);
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/*
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* Reverse engineered from a dump of the floppy drive's ROM. I have no idea how
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* it works.
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*
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* LF8BA:
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* clra
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* staa X00B0
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* staa X00B1
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* ldx #$8000
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* LF8C2: ldaa $00,x
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* inx
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* bsr LF8CF
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* cpx #$8011
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* bne LF8C2
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* ldd X00B0
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* rts
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* LF8CF:
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* eora X00B0
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* staa X00CF
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* asla
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* asla
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* asla
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* asla
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* eora X00CF
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* staa X00CF
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* rola
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* rola
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* rola
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* tab
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* anda #$F8
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* eora X00B1
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* staa X00B0
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* rolb
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* rolb
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* andb #$0F
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* eorb X00B0
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* stab X00B0
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* rolb
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* eorb X00CF
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* stab X00B1
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* rts
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*/
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static void rol(uint8_t& b, bool& c)
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{
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bool newc = b & 0x80;
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b <<= 1;
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b |= c;
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c = newc;
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}
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static uint16_t checksum(const Bytes& bytes)
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{
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uint8_t crclo = 0;
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uint8_t crchi = 0;
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for (uint8_t a : bytes)
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{
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a ^= crchi;
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uint8_t t1 = a;
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a <<= 4;
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bool c = a & 0x10;
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a ^= t1;
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t1 = a;
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rol(a, c);
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rol(a, c);
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rol(a, c);
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uint8_t b = a;
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a &= 0xf8;
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a ^= crclo;
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crchi = a;
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rol(b, c);
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rol(b, c);
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b &= 0x0f;
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b ^= crchi;
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crchi = b;
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rol(b, c);
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b ^= t1;
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crclo = b;
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}
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return (crchi << 8) | crclo;
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}
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AbstractDecoder::RecordType Fb100Decoder::advanceToNextRecord()
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{
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const FluxMatcher* matcher = nullptr;
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_sector->clock = _fmr->seekToPattern(SECTOR_ID_PATTERN, matcher);
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if (matcher == &SECTOR_ID_PATTERN)
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return RecordType::SECTOR_RECORD;
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return RecordType::UNKNOWN_RECORD;
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}
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void Fb100Decoder::decodeSectorRecord()
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{
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auto rawbits = readRawBits(FB100_RECORD_SIZE*16);
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const Bytes bytes = decodeFmMfm(rawbits).slice(0, FB100_RECORD_SIZE);
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ByteReader br(bytes);
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br.seek(1);
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const Bytes id = br.read(FB100_ID_SIZE);
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uint16_t wantIdCrc = br.read_be16();
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uint16_t gotIdCrc = checksum(id);
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const Bytes payload = br.read(FB100_PAYLOAD_SIZE);
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uint16_t wantPayloadCrc = br.read_be16();
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uint16_t gotPayloadCrc = checksum(payload);
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if (wantIdCrc != gotIdCrc)
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return;
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uint8_t abssector = id[2];
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_sector->logicalTrack = abssector >> 1;
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_sector->logicalSide = 0;
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_sector->logicalSector = abssector & 1;
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_sector->data.writer().append(id.slice(5, 12)).append(payload);
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_sector->status = (wantPayloadCrc == gotPayloadCrc) ? Sector::OK : Sector::BAD_CHECKSUM;
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} |