// license:BSD-3-Clause
// copyright-holders:Antoine Mine
/**********************************************************************
Copyright (C) Antoine Mine' 2007
Motorola 6843 Floppy Disk Controller emulation.
**********************************************************************/
/*
Main MC 6843 features are:
- single density floppies
- IBM 3740 compatible
- DMA-able
- high-level commands (including multi-sector read/write)
CLONES: HD 46503S seems to be a clone of MC 6843
BUGS
The driver was designed with Thomson computer emulation in mind
(CD 90-015 5"1/4 floppy controller) and works in this context.
It might work in other contexts but has currently shortcomings:
- DMA is not emulated
- Free-Format Read is not emulated
- Free-Format Write only supports track formatting, in a specific
format (FWF=1, Thomson-like sector formats)
- very rough timing: basically, there is a fixed delay between
a command request (CMR write) and its response (first byte
available, seek complete, etc.); there is no delay between
read / write
*/
#include "emu.h"
#include "mc6843.h"
//#define VERBOSE 1
#include "logmacro.h"
/******************* parameters ******************/
/* macro-command numbers */
#define CMD_STZ 0x2 /* seek track zero */
#define CMD_SEK 0x3 /* seek */
#define CMD_SSR 0x4 /* single sector read */
#define CMD_SSW 0x5 /* single sector write */
#define CMD_RCR 0x6 /* read CRC */
#define CMD_SWD 0x7 /* single sector write with delete data mark */
#define CMD_MSW 0xd /* multiple sector write */
#define CMD_MSR 0xc /* multiple sector read */
#define CMD_FFW 0xb /* free format write */
#define CMD_FFR 0xa /* free format read */
/* coarse delays */
#define DELAY_SEEK attotime::from_usec( 100 ) /* track seek time */
#define DELAY_ADDR attotime::from_usec( 100 ) /* search-address time */
static const char *const mc6843_cmd[16] =
{
"---", "---", "STZ", "SEK", "SSR", "SSW", "RCR", "SWD",
"---", "---", "FFR", "FFW", "MSR", "MSW", "---", "---",
};
DEFINE_DEVICE_TYPE(MC6843, mc6843_device, "mc5843", "Motorola MC6843 FDC")
mc6843_device::mc6843_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
: device_t(mconfig, MC6843, tag, owner, clock),
m_write_irq(*this),
m_CTAR(0),
m_CMR(0),
m_ISR(0),
m_SUR(0),
m_STRA(0),
m_STRB(0),
m_SAR(0),
m_GCR(0),
m_CCR(0),
m_LTAR(0),
m_drive(0),
m_side(0),
m_data_size(0),
m_data_idx(0),
m_data_id(0),
m_index_pulse(0),
m_timer_cont(nullptr)
{
for (auto & elem : m_data)
{
elem = 0;
}
}
//-------------------------------------------------
// device_start - device-specific startup
//-------------------------------------------------
void mc6843_device::device_start()
{
m_write_irq.resolve_safe();
m_timer_cont = timer_alloc(TIMER_CONT);
save_item(NAME(m_CTAR));
save_item(NAME(m_CMR));
save_item(NAME(m_ISR));
save_item(NAME(m_SUR));
save_item(NAME(m_STRA));
save_item(NAME(m_STRB));
save_item(NAME(m_SAR));
save_item(NAME(m_GCR));
save_item(NAME(m_CCR));
save_item(NAME(m_LTAR));
save_item(NAME(m_drive));
save_item(NAME(m_side));
save_item(NAME(m_data));
save_item(NAME(m_data_size));
save_item(NAME(m_data_idx));
save_item(NAME(m_data_id));
}
//-------------------------------------------------
// device_reset - device-specific reset
//-------------------------------------------------
void mc6843_device::device_reset()
{
int i;
LOG (( "mc6843 reset\n" ));
/* setup/reset floppy drive */
for ( i = 0; i < 4; i++ )
{
legacy_floppy_image_device * img = floppy_image( i );
img->floppy_mon_w(CLEAR_LINE);
img->floppy_drive_set_ready_state(FLOPPY_DRIVE_READY, 0 );
img->floppy_drive_set_rpm( 300. );
}
/* reset registers */
m_CMR &= 0xf0; /* zero only command */
m_ISR = 0;
m_STRA &= 0x5c;
m_SAR = 0;
m_STRB &= 0x20;
status_update( );
m_data_size = 0;
m_data_idx = 0;
m_timer_cont->adjust( attotime::never );
}
/************************** floppy interface ****************************/
legacy_floppy_image_device* mc6843_device::floppy_image( uint8_t drive )
{
legacy_floppy_image_device *img = floppy_get_device( machine(), drive );
if (!img && owner()) {
// For slot devices, drives are typically attached to the slot rather than the machine
const char *floppy_name = nullptr;
switch (drive) {
case 0:
floppy_name = FLOPPY_0;
break;
case 1:
floppy_name = FLOPPY_1;
break;
case 2:
floppy_name = FLOPPY_2;
break;
case 3:
floppy_name = FLOPPY_3;
break;
}
img = owner()->subdevice<legacy_floppy_image_device>(floppy_name);
}
return img;
}
legacy_floppy_image_device* mc6843_device::floppy_image( )
{
return floppy_image( m_drive );
}
void mc6843_device::set_drive( int drive )
{
m_drive = drive;
}
void mc6843_device::set_side( int side )
{
m_side = side;
}
/* called after ISR or STRB has changed */
void mc6843_device::status_update( )
{
int irq = 0;
/* ISR3 */
if ( (m_CMR & 0x40) || ! m_STRB )
m_ISR &= ~8;
else
m_ISR |= 8;
/* interrupts */
if ( m_ISR & 4 )
irq = 1; /* unmaskable */
if ( ! (m_CMR & 0x80) )
{
/* maskable */
if ( m_ISR & ~4 )
irq = 1;
}
m_write_irq( irq );
LOG( "status_update: irq=%i (CMR=%02X, ISR=%02X)\n", irq, m_CMR, m_ISR );
}
void mc6843_device::set_index_pulse( int index_pulse )
{
m_index_pulse = index_pulse;
}
/* called at end of command */
void mc6843_device::cmd_end( )
{
int cmd = m_CMR & 0x0f;
if ( ( cmd == CMD_STZ ) || ( cmd == CMD_SEK ) )
{
m_ISR |= 0x02; /* set Settling Time Complete */
}
else
{
m_ISR |= 0x01; /* set Macro Command Complete */
}
m_STRA &= ~0x80; /* clear Busy */
m_CMR &= 0xf0; /* clear command */
status_update( );
}
/* Seek Track Zero bottom half */
void mc6843_device::finish_STZ( )
{
legacy_floppy_image_device* img = floppy_image( );
int i;
/* seek to track zero */
for ( i=0; i<83; i++ )
{
if (img->floppy_tk00_r() == CLEAR_LINE)
break;
img->floppy_drive_seek( -1 );
}
LOG( "%f mc6843_finish_STZ: actual=%i\n", machine().time().as_double(), img->floppy_drive_get_current_track() );
/* update state */
m_CTAR = 0;
m_GCR = 0;
m_SAR = 0;
m_STRB |= img->floppy_tk00_r() << 4;
cmd_end( );
}
/* Seek bottom half */
void mc6843_device::finish_SEK( )
{
legacy_floppy_image_device* img = floppy_image( );
/* seek to track */
// TODO: not sure how CTAR bit 7 is handled here, but this is the safest approach for now
img->floppy_drive_seek( m_GCR - (m_CTAR & 0x7F) );
LOG( "%f mc6843_finish_SEK: from %i to %i (actual=%i)\n", machine().time().as_double(), (m_CTAR & 0x7F), m_GCR, img->floppy_drive_get_current_track() );
/* update state */
m_CTAR = m_GCR;
m_SAR = 0;
cmd_end( );
}
/* preamble to all sector read / write commands, returns 1 if found */
int mc6843_device::address_search( chrn_id* id )
{
legacy_floppy_image_device* img = floppy_image( );
int r = 0;
while ( 1 )
{
if ( ( ! img->floppy_drive_get_next_id( m_side, id ) ) || ( id->flags & ID_FLAG_CRC_ERROR_IN_ID_FIELD ) || ( id->N != 0 ) )
{
/* read address error */
LOG( "%f mc6843_address_search: get_next_id failed\n", machine().time().as_double() );
m_STRB |= 0x0a; /* set CRC error & Sector Address Undetected */
cmd_end( );
return 0;
}
if ( id->C != m_LTAR )
{
/* track mismatch */
LOG( "%f mc6843_address_search: track mismatch: logical=%i real=%i\n", machine().time().as_double(), m_LTAR, id->C );
m_data[0] = id->C; /* make the track number available to the CPU */
m_STRA |= 0x20; /* set Track Not Equal */
cmd_end( );
return 0;
}
if ( id->R == m_SAR )
{
/* found! */
LOG( "%f mc6843_address_search: sector %i found on track %i\n", machine().time().as_double(), id->R, id->C );
if ( ! (m_CMR & 0x20) )
{
m_ISR |= 0x04; /* if no DMA, set Status Sense */
}
return 1;
}
if ( img->floppy_drive_get_flag_state( FLOPPY_DRIVE_INDEX ) )
{
r++;
if ( r >= 4 )
{
/* time-out after 3 full revolutions */
LOG( "%f mc6843_address_search: no sector %i found after 3 revolutions\n", machine().time().as_double(), m_SAR );
m_STRB |= 0x08; /* set Sector Address Undetected */
cmd_end( );
return 0;
}
}
}
//return 0; /* unreachable */
}
/* preamble specific to read commands (adds extra checks) */
int mc6843_device::address_search_read( chrn_id* id )
{
if ( ! address_search( id ) )
return 0;
if ( id->flags & ID_FLAG_CRC_ERROR_IN_DATA_FIELD )
{
LOG( "%f mc6843_address_search_read: data CRC error\n", machine().time().as_double() );
m_STRB |= 0x06; /* set CRC error & Data Mark Undetected */
cmd_end( );
return 0;
}
if ( id->flags & ID_FLAG_DELETED_DATA )
{
LOG( "%f mc6843_address_search_read: deleted data\n", machine().time().as_double() );
m_STRA |= 0x02; /* set Delete Data Mark Detected */
}
return 1;
}
/* Read CRC bottom half */
void mc6843_device::finish_RCR( )
{
chrn_id id;
if ( ! address_search_read( &id ) )
return;
cmd_end( );
}
/* Single / Multiple Sector Read bottom half */
void mc6843_device::cont_SR( )
{
chrn_id id;
legacy_floppy_image_device* img = floppy_image( );
/* sector seek */
if ( ! address_search_read( &id ) )
return;
/* sector read */
img->floppy_drive_read_sector_data( m_side, id.data_id, m_data, 128 );
m_data_idx = 0;
m_data_size = 128;
m_STRA |= 0x01; /* set Data Transfer Request */
status_update( );
}
/* Single / Multiple Sector Write bottom half */
void mc6843_device::cont_SW( )
{
chrn_id id;
/* sector seek */
if ( ! address_search( &id ) )
return;
/* setup sector write buffer */
m_data_idx = 0;
m_data_size = 128;
m_STRA |= 0x01; /* set Data Transfer Request */
m_data_id = id.data_id; /* for subsequent write sector command */
status_update( );
}
/* bottom halves, called to continue / finish a command after some delay */
void mc6843_device::device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr)
{
switch (id)
{
case TIMER_CONT:
{
int cmd = m_CMR & 0x0f;
LOG( "%f mc6843_cont: timer called for cmd=%s(%i)\n", machine().time().as_double(), mc6843_cmd[cmd], cmd );
m_timer_cont->adjust( attotime::never );
switch ( cmd )
{
case CMD_STZ: finish_STZ( ); break;
case CMD_SEK: finish_SEK( ); break;
case CMD_SSR: cont_SR( ); break;
case CMD_SSW: cont_SW( ); break;
case CMD_RCR: finish_RCR( ); break;
case CMD_SWD: cont_SW( ); break;
case CMD_MSW: cont_SW( ); break;
case CMD_MSR: cont_SR( ); break;
}
}
break;
default:
break;
}
}
/************************** CPU interface ****************************/
READ8_MEMBER( mc6843_device::read )
{
uint8_t data = 0;
switch ( offset ) {
case 0: /* Data Input Register (DIR) */
{
int cmd = m_CMR & 0x0f;
LOG( "%f %s mc6843_r: data input cmd=%s(%i), pos=%i/%i, GCR=%i, ",
machine().time().as_double(), machine().describe_context(),
mc6843_cmd[cmd], cmd, m_data_idx,
m_data_size, m_GCR );
if ( cmd == CMD_SSR || cmd == CMD_MSR )
{
/* sector read */
assert( m_data_size > 0 );
assert( m_data_idx < m_data_size );
assert( m_data_idx < sizeof(m_data) );
data = m_data[ m_data_idx ];
m_data_idx++;
if ( m_data_idx >= m_data_size )
{
/* end of sector read */
m_STRA &= ~0x01; /* clear Data Transfer Request */
if ( cmd == CMD_MSR )
{
/* schedule next sector in multiple sector read */
m_GCR--;
m_SAR++;
if ( m_GCR == 0xff )
{
cmd_end( );
}
else if ( m_SAR > 26 )
{
m_STRB |= 0x08; /* set Sector Address Undetected */
cmd_end( );
}
else
{
m_timer_cont->adjust( DELAY_ADDR );
}
}
else
{
cmd_end( );
}
}
}
else if ( cmd == 0 )
{
data = m_data[0];
}
else
{
/* XXX TODO: other read modes */
data = m_data[0];
logerror( "%s mc6843 read in unsupported command mode %i\n", machine().describe_context(), cmd );
}
LOG( "data=%02X\n", data );
break;
}
case 1: /* Current-Track Address Register (CTAR) */
data = m_CTAR;
LOG( "%f %s mc6843_r: read CTAR %i (actual=%i)\n",
machine().time().as_double(), machine().describe_context(), data,
floppy_image()->floppy_drive_get_current_track());
break;
case 2: /* Interrupt Status Register (ISR) */
data = m_ISR;
LOG( "%f %s mc6843_r: read ISR %02X: cmd=%scomplete settle=%scomplete sense-rq=%i STRB=%i\n",
machine().time().as_double(), machine().describe_context(), data,
(data & 1) ? "" : "not-" , (data & 2) ? "" : "not-",
(data >> 2) & 1, (data >> 3) & 1 );
/* reset */
m_ISR &= 8; /* keep STRB */
status_update( );
break;
case 3: /* Status Register A (STRA) */
{
/* update */
legacy_floppy_image_device* img = floppy_image( );
int flag = img->floppy_drive_get_flag_state( FLOPPY_DRIVE_READY);
m_STRA &= 0xa3;
if ( flag & FLOPPY_DRIVE_READY )
m_STRA |= 0x04;
m_STRA |= !img->floppy_tk00_r() << 3;
m_STRA |= !img->floppy_wpt_r() << 4;
if ( m_index_pulse )
m_STRA |= 0x40;
data = m_STRA;
LOG( "%f %s mc6843_r: read STRA %02X: data-rq=%i del-dta=%i ready=%i t0=%i wp=%i trk-dif=%i idx=%i busy=%i\n",
machine().time().as_double(), machine().describe_context(), data,
data & 1, (data >> 1) & 1, (data >> 2) & 1, (data >> 3) & 1,
(data >> 4) & 1, (data >> 5) & 1, (data >> 6) & 1, (data >> 7) & 1 );
break;
}
case 4: /* Status Register B (STRB) */
data = m_STRB;
LOG( "%f %s mc6843_r: read STRB %02X: data-err=%i CRC-err=%i dta--mrk-err=%i sect-mrk-err=%i seek-err=%i fi=%i wr-err=%i hard-err=%i\n",
machine().time().as_double(), machine().describe_context(), data,
data & 1, (data >> 1) & 1, (data >> 2) & 1, (data >> 3) & 1,
(data >> 4) & 1, (data >> 5) & 1, (data >> 6) & 1, (data >> 7) & 1 );
/* (partial) reset */
m_STRB &= ~0xfb;
status_update( );
break;
case 7: /* Logical-Track Address Register (LTAR) */
data = m_LTAR;
LOG( "%f %s mc6843_r: read LTAR %i (actual=%i)\n",
machine().time().as_double(), machine().describe_context(), data,
floppy_image()->floppy_drive_get_current_track());
break;
default:
logerror( "%s mc6843 invalid read offset %i\n", machine().describe_context(), offset );
}
return data;
}
WRITE8_MEMBER( mc6843_device::write )
{
switch ( offset ) {
case 0: /* Data Output Register (DOR) */
{
int cmd = m_CMR & 0x0f;
int FWF = (m_CMR >> 4) & 1;
LOG( "%f %s mc6843_w: data output cmd=%s(%i), pos=%i/%i, GCR=%i, data=%02X\n",
machine().time().as_double(), machine().describe_context(),
mc6843_cmd[cmd], cmd, m_data_idx,
m_data_size, m_GCR, data );
if ( cmd == CMD_SSW || cmd == CMD_MSW || cmd == CMD_SWD )
{
/* sector write */
assert( m_data_size > 0 );
assert( m_data_idx < m_data_size );
assert( m_data_idx < sizeof(m_data) );
m_data[ m_data_idx ] = data;
m_data_idx++;
if ( m_data_idx >= m_data_size )
{
/* end of sector write */
legacy_floppy_image_device* img = floppy_image( );
LOG( "%f %s mc6843_w: write sector %i\n", machine().time().as_double(), machine().describe_context(), m_data_id );
img->floppy_drive_write_sector_data(
m_side, m_data_id,
m_data, m_data_size,
(cmd == CMD_SWD) ? ID_FLAG_DELETED_DATA : 0 );
m_STRA &= ~0x01; /* clear Data Transfer Request */
if ( cmd == CMD_MSW )
{
m_GCR--;
m_SAR++;
if ( m_GCR == 0xff )
{
cmd_end( );
}
else if ( m_SAR > 26 )
{
m_STRB |= 0x08; /* set Sector Address Undetected */
cmd_end( );
}
else
{
m_timer_cont->adjust( DELAY_ADDR );
}
}
else
{
cmd_end( );
}
}
}
else if ( (cmd == CMD_FFW) && FWF )
{
/* assume we are formatting */
uint8_t nibble;
nibble =
(data & 0x01) |
((data & 0x04) >> 1 )|
((data & 0x10) >> 2 )|
((data & 0x40) >> 3 );
assert( m_data_idx < sizeof(m_data) );
m_data[m_data_idx / 2] =
(m_data[m_data_idx / 2] << 4) | nibble;
if ( (m_data_idx == 0) && (m_data[0] == 0xfe ) )
{
/* address mark detected */
m_data_idx = 2;
}
else if ( m_data_idx == 9 )
{
/* address id field complete */
if ( (m_data[2] == 0) && (m_data[4] == 0) )
{
/* valid address id field */
legacy_floppy_image_device* img = floppy_image( );
uint8_t track = m_data[1];
uint8_t sector = m_data[3];
uint8_t filler = 0xe5; /* standard Thomson filler */
LOG( "%f %s mc6843_w: address id detected track=%i sector=%i\n", machine().time().as_double(), machine().describe_context(), track, sector);
img->floppy_drive_format_sector( m_side, sector, track, 0, sector, 0, filler );
}
else
{
/* abort */
m_data_idx = 0;
}
}
else if ( m_data_idx > 0 )
{
/* accumulate address id field */
m_data_idx++;
}
}
else if ( cmd == 0 )
{
/* nothing */
}
else
{
/* XXX TODO: other write modes */
logerror( "%s mc6843 write %02X in unsupported command mode %i (FWF=%i)\n", machine().describe_context(), data, cmd, FWF );
}
break;
}
case 1: /* Current-Track Address Register (CTAR) */
m_CTAR = data;
LOG( "%f %s mc6843_w: set CTAR to %i %02X (actual=%i) \n",
machine().time().as_double(), machine().describe_context(), m_CTAR, data,
floppy_image()->floppy_drive_get_current_track());
break;
case 2: /* Command Register (CMR) */
{
int cmd = data & 15;
LOG( "%f %s mc6843_w: set CMR to $%02X: cmd=%s(%i) FWF=%i DMA=%i ISR3-intr=%i fun-intr=%i\n",
machine().time().as_double(), machine().describe_context(),
data, mc6843_cmd[cmd], cmd, (data >> 4) & 1, (data >> 5) & 1,
(data >> 6) & 1, (data >> 7) & 1 );
/* sanitize state */
m_STRA &= ~0x81; /* clear Busy & Data Transfer Request */
m_data_idx = 0;
m_data_size = 0;
/* commands are initiated by updating some flags and scheduling
a bottom-half (mc6843_cont) after some delay */
switch (cmd)
{
case CMD_SSW:
case CMD_SSR:
case CMD_SWD:
case CMD_RCR:
case CMD_MSR:
case CMD_MSW:
m_STRA |= 0x80; /* set Busy */
m_STRA &= ~0x22; /* clear Track Not Equal & Delete Data Mark Detected */
m_STRB &= ~0x04; /* clear Data Mark Undetected */
m_timer_cont->adjust( DELAY_ADDR );
break;
case CMD_STZ:
case CMD_SEK:
m_STRA |= 0x80; /* set Busy */
m_timer_cont->adjust( DELAY_SEEK );
break;
case CMD_FFW:
case CMD_FFR:
m_data_idx = 0;
m_STRA |= 0x01; /* set Data Transfer Request */
break;
}
m_CMR = data;
status_update( );
break;
}
case 3: /* Set-Up Register (SUR) */
m_SUR = data;
/* assume CLK freq = 1MHz (IBM 3740 compatibility) */
LOG( "%f %s mc6843_w: set SUR to $%02X: head settling time=%fms, track-to-track seek time=%f\n",
machine().time().as_double(), machine().describe_context(),
data, 4.096 * (data & 15), 1.024 * ((data >> 4) & 15) );
break;
case 4: /* Sector Address Register (SAR) */
m_SAR = data & 0x1f;
LOG( "%f %s mc6843_w: set SAR to %i (%02X)\n", machine().time().as_double(), machine().describe_context(), m_SAR, data );
break;
case 5: /* General Count Register (GCR) */
m_GCR = data & 0x7f;
LOG( "%f %s mc6843_w: set GCR to %i (%02X)\n", machine().time().as_double(), machine().describe_context(), m_GCR, data );
break;
case 6: /* CRC Control Register (CCR) */
m_CCR = data & 3;
LOG( "%f %s mc6843_w: set CCR to %02X: CRC=%s shift=%i\n",
machine().time().as_double(), machine().describe_context(), data,
(data & 1) ? "enabled" : "disabled", (data >> 1) & 1 );
break;
case 7: /* Logical-Track Address Register (LTAR) */
m_LTAR = data & 0x7f;
LOG( "%f %s mc6843_w: set LTAR to %i %02X (actual=%i)\n",
machine().time().as_double(), machine().describe_context(), m_LTAR, data,
floppy_image()->floppy_drive_get_current_track());
break;
default:
logerror( "%s mc6843 invalid write offset %i (data=$%02X)\n", machine().describe_context(), offset, data );
}
}