swim_asm.S
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/*
* low-level functions for the SWIM floppy controller
*
* needs assembly language because is very timing dependent
* this controller exists only on macintosh 680x0 based
*
* Copyright (C) 2004,2008 Laurent Vivier <Laurent@lvivier.info>
*
* based on Alastair Bridgewater SWIM analysis, 2001
* based on netBSD IWM driver (c) 1997, 1998 Hauke Fath.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* 2004-08-21 (lv) - Initial implementation
* 2008-11-05 (lv) - add get_swim_mode
*/
.equ write_data, 0x0000
.equ write_mark, 0x0200
.equ write_CRC, 0x0400
.equ write_parameter,0x0600
.equ write_phase, 0x0800
.equ write_setup, 0x0a00
.equ write_mode0, 0x0c00
.equ write_mode1, 0x0e00
.equ read_data, 0x1000
.equ read_mark, 0x1200
.equ read_error, 0x1400
.equ read_parameter, 0x1600
.equ read_phase, 0x1800
.equ read_setup, 0x1a00
.equ read_status, 0x1c00
.equ read_handshake, 0x1e00
.equ o_side, 0
.equ o_track, 1
.equ o_sector, 2
.equ o_size, 3
.equ o_crc0, 4
.equ o_crc1, 5
.equ seek_time, 30000
.equ max_retry, 40
.equ sector_size, 512
.global swim_read_sector_header
swim_read_sector_header:
link %a6, #0
moveml %d1-%d5/%a0-%a4,%sp@-
movel %a6@(0x0c), %a4
bsr mfm_read_addrmark
moveml %sp@+, %d1-%d5/%a0-%a4
unlk %a6
rts
sector_address_mark:
.byte 0xa1, 0xa1, 0xa1, 0xfe
sector_data_mark:
.byte 0xa1, 0xa1, 0xa1, 0xfb
mfm_read_addrmark:
movel %a6@(0x08), %a3
lea %a3@(read_handshake), %a2
lea %a3@(read_mark), %a3
moveq #-1, %d0
movew #seek_time, %d2
wait_header_init:
tstb %a3@(read_error - read_mark)
moveb #0x18, %a3@(write_mode0 - read_mark)
moveb #0x01, %a3@(write_mode1 - read_mark)
moveb #0x01, %a3@(write_mode0 - read_mark)
tstb %a3@(read_error - read_mark)
moveb #0x08, %a3@(write_mode1 - read_mark)
lea sector_address_mark, %a0
moveq #3, %d1
wait_addr_mark_byte:
tstb %a2@
dbmi %d2, wait_addr_mark_byte
bpl header_exit
moveb %a3@, %d3
cmpb %a0@+, %d3
dbne %d1, wait_addr_mark_byte
bne wait_header_init
moveq #max_retry, %d2
amark0: tstb %a2@
dbmi %d2, amark0
bpl signal_nonyb
moveb %a3@, %a4@(o_track)
moveq #max_retry, %d2
amark1: tstb %a2@
dbmi %d2, amark1
bpl signal_nonyb
moveb %a3@, %a4@(o_side)
moveq #max_retry, %d2
amark2: tstb %a2@
dbmi %d2, amark2
bpl signal_nonyb
moveb %a3@, %a4@(o_sector)
moveq #max_retry, %d2
amark3: tstb %a2@
dbmi %d2, amark3
bpl signal_nonyb
moveb %a3@, %a4@(o_size)
moveq #max_retry, %d2
crc0: tstb %a2@
dbmi %d2, crc0
bpl signal_nonyb
moveb %a3@, %a4@(o_crc0)
moveq #max_retry, %d2
crc1: tstb %a2@
dbmi %d2, crc1
bpl signal_nonyb
moveb %a3@, %a4@(o_crc1)
tstb %a3@(read_error - read_mark)
header_exit:
moveq #0, %d0
moveb #0x18, %a3@(write_mode0 - read_mark)
rts
signal_nonyb:
moveq #-1, %d0
moveb #0x18, %a3@(write_mode0 - read_mark)
rts
.global swim_read_sector_data
swim_read_sector_data:
link %a6, #0
moveml %d1-%d5/%a0-%a5,%sp@-
movel %a6@(0x0c), %a4
bsr mfm_read_data
moveml %sp@+, %d1-%d5/%a0-%a5
unlk %a6
rts
mfm_read_data:
movel %a6@(0x08), %a3
lea %a3@(read_handshake), %a2
lea %a3@(read_data), %a5
lea %a3@(read_mark), %a3
movew #seek_time, %d2
wait_data_init:
tstb %a3@(read_error - read_mark)
moveb #0x18, %a3@(write_mode0 - read_mark)
moveb #0x01, %a3@(write_mode1 - read_mark)
moveb #0x01, %a3@(write_mode0 - read_mark)
tstb %a3@(read_error - read_mark)
moveb #0x08, %a3@(write_mode1 - read_mark)
lea sector_data_mark, %a0
moveq #3, %d1
/* wait data address mark */
wait_data_mark_byte:
tstb %a2@
dbmi %d2, wait_data_mark_byte
bpl data_exit
moveb %a3@, %d3
cmpb %a0@+, %d3
dbne %d1, wait_data_mark_byte
bne wait_data_init
/* read data */
tstb %a3@(read_error - read_mark)
movel #sector_size-1, %d4 /* sector size */
read_new_data:
movew #max_retry, %d2
read_data_loop:
moveb %a2@, %d5
andb #0xc0, %d5
dbne %d2, read_data_loop
beq data_exit
moveb %a5@, %a4@+
andb #0x40, %d5
dbne %d4, read_new_data
beq exit_loop
moveb %a5@, %a4@+
dbra %d4, read_new_data
exit_loop:
/* read CRC */
movew #max_retry, %d2
data_crc0:
tstb %a2@
dbmi %d2, data_crc0
bpl data_exit
moveb %a3@, %d5
moveq #max_retry, %d2
data_crc1:
tstb %a2@
dbmi %d2, data_crc1
bpl data_exit
moveb %a3@, %d5
tstb %a3@(read_error - read_mark)
moveb #0x18, %a3@(write_mode0 - read_mark)
/* return number of bytes read */
movel #sector_size, %d0
addw #1, %d4
subl %d4, %d0
rts
data_exit:
moveb #0x18, %a3@(write_mode0 - read_mark)
moveq #-1, %d0
rts