OswFFv2.src

10 REM > OswFFv2/src

20 REM Source for OSWORD &FF v1.02

30 REM Accesses sideways ROMs and shadow screen memory

40 REM Adapts to Electron ROMSEL and Tube

50 :

60 REM OSWORD &FF transfers blocks of memory between I/O and CoPro memory

70 REM X%?0 =&0D

80 REM X%?1 =&01

90 REM X%!2 =I/O address

100 REM X%!6 =CoPro address

110 REM X%!10=Number of bytes to transfer

120 REM X%?12=0 for C->H, =1 for H->C

130 :

140 REM I/O address can be:

150 REM &FFxRxxxx for ROM R

160 REM &FF8xxxxx for workspace RAM

170 REM &FFFFxxxx for I/O memory

180 REM &FFFExxxx for current display memory

190 REM &FFFDxxxx for shadow display memory

200 :

210 OS_CLI=&FFF7:OSBYTE=&FFF4:OSWORD=&FFF1:OSWRCH=&FFEE

220 OSWRCR=&FFEC:OSNEWL=&FFE7:OSASCI=&FFE3:OSRDCH=&FFE0

230 USERV=&200

240 :

250 ctrl=&70:saveA=&72:unused=&73:addr=&74:count=&76

260 :

270 run%=&FFFF2500:load%=&FFFF0900

280 DIM mcode% &180

290 FOR P=0 TO 1

300 P%=run%:O%=mcode%

310 [OPT P*3+4

320 .L2500

330 JMP L2505 :\ New USER entry

340 .OldUSERV

350 EQUW L2500 :\ Swapped with USERV to claim

360 .L2505

370 CMP #&FF:BEQ L250C :\ If my OSWORD, jump to respond

380 JMP (OldUSERV) :\ Continue via OldUSERV

390 :

400 .L250C

410 STX ctrl+0:STY ctrl+1:PHA :\ Save OSWORD parameters

420 LDA &F4:PHA :\ Save current ROM

430 LDA &FFB2:EOR #&BC :\ Check for Electron, has to be done

440 CMP #&FC:BNE GetAddress :\ inline as no initialisation call

450 STA TUBEIO1+2:STA TUBEIO2+2 :\ Change to Electron TUBEIO

460 LDA #5:STA ROMSEL+1 :\ Change to Electron ROMSEL

470 :

480 .GetAddress

490 LDY #&02:LDA (ctrl),Y:STA addr+0 :\ I/O address low byte

500 INY:LDA (ctrl),Y:STA addr+1 :\ I/O address high byte

510 INY:LDA (ctrl),Y:TAX :\ I/O address ROM/screen byte

520 CLC:ADC #&40 :\ Allow &0x and &Fx for ROMs

530 JSR ROMSelect :\ Page in ROM

540 INX:BEQ GetIOMem :\ &FFFFxxxx - I/O memory

550 INX:BEQ GetDisplay :\ &FFFExxxx - current screen

560 INX:BEQ GetShadow :\ &FFFDxxxx - shadow memory

570 BNE GetIOMem

580 :

590 .GetDisplay

600 LDA #&84:JSR OSBYTE

610 TYA:BPL GetIOMem :\ Not shadow screen displayed

620 .GetShadow

630 LDA #1:JSR vramSelect

640 :

650 .GetIOMem

660 .TubeClaim

670 LDA #&C0+7:JSR &0406 :\ Claim the Tube with ID=7

680 BCC TubeClaim :\ Loop until claimed

690 LDY #&0C:LDA (ctrl),Y:PHA :\ Get read/write command

700 LDA ctrl+0:CLC:ADC #&06:TAX :\ Point to Control+6

710 LDA #&00:ADC ctrl+1:TAY :\ XY->CoPro address in control block

720 PLA:PHA:JSR &406 :\ Initiate specified action

730 LDY #&0A:LDA (ctrl),Y:TAX :\ Get X=count low byte

740 INY:LDA (ctrl),Y:STA count :\ Get count high byte

750 BNE L2544 :\ Jump forward if >255 bytes to do

760 TXA:BEQ L2592 :\ Jump to exit if no bytes to do

770 .L2544

780 TXA:BEQ L2549 :\ Jump forward if multiple of 256 bytes

790 INC count :\ Inc high byte to balance DECs later

800 .L2549

810 LDY #&00 :\ Prepare zero offset for (zp),Y

820 PLA:ROR A:BCS L2577 :\ Get command back, jump if H->C

830 :

840 \ Copy from Client to Host

850 \ ------------------------

860 .L2558

870 JSR TubeDelay :\ Delay before start and between bytes

880 .TUBEIO1

890 LDA &FEE5:STA (addr),Y :\ Transfer a byte C->H

900 INC addr+0:BNE L256C:INC addr+1 :\ Update I/O address

910 .L256C

920 DEX:BNE L2558 :\ Loop for sub-256 byte count

930 DEC count:BNE L2558 :\ Loop for each 256-byte chunk

940 BEQ L2592 :\ Jump to exit when finished

950 :

960 \ Copy from Host to Client

970 \ ------------------------

980 .L2577

990 LDA (addr),Y

1000 .TUBEIO2

1010 STA &FEE5 :\ Transfer byte H->C

1020 JSR TubeDelay :\ Delay between bytes

1030 INC addr+0:BNE L258B:INC addr+1 :\ Update I/O address

1040 .L258B

1050 DEX:BNE L2577 :\ Loop for sub-256 byte count

1060 DEC count:BNE L2577 :\ Loop for each 256-byte chunk

1070 :

1080 \ Release and return

1090 \ ------------------

1100 .L2592

1110 LDA #&80+7:JSR &0406 :\ Release Tube with ID=7

1120 LDA #0:JSR vramSelect :\ Page main memory back in

1130 PLA:JSR ROMSelect :\ Restore ROM

1140 LDX ctrl+0:LDY ctrl+1:PLA :\ Restore entry registers

1150 RTS :\ And return

1160 :

1170 .TubeDelay :JSR TubeDelay2 :\ 24us between Tube accesses

1180 .TubeDelay2:JSR TubeDelay3

1190 .TubeDelay3:RTS

1200 :

1210 .ROMSelect

1220 PHA:LDA #12:JSR ROMSelect2:PLA :\ Double select for Electron

1230 .ROMSelect2

1240 STA &F4

1250 .ROMSEL

1260 STA &FE30

1270 .vramOk

1280 RTS

1290 :

1300 .vramSelect

1310 PHA:TAX :\ A=0 main RAM, A=1 video RAM

1320 LDA #108:JSR OSBYTE :\ Attempt to select Master video RAM

1330 PLA:INX:BNE vramOk :\ X<>255, successful

1340 EOR #1:TAX :\ A=1 main RAM, A=0 video RAM

1350 LDA #111:JMP OSBYTE :\ Attempt to select Aries/Watford RAM

1360 .end%

1370

1380 ]:P%=P%-run%+load%:off%=run%-load%:[OPT P*3+4

1390 :

1400 \ This code allows OSWORD &FF to live in a *runnable program

1410 \ Can be *RUN on top of itself or on top of other code at &2500

1420 :

1430 .exec%

1440 PHP:SEI :\ Prevent IRQs while changing vectors

1450 BIT &27A:BPL SetupExit :\ No Tube present

1460 LDA USERV+1:CMP OldUSERV-off%+1:BNE Setup :\ Not linked to me, claim it

1470 LDA USERV+0:CMP OldUSERV-off%+0:BNE Setup :\ Not linked to me, claim it

1480 LDA OldUSERV+1:STA USERV+1 :\ Already linked, restore USERV

1490 LDA OldUSERV+0:STA USERV+0 :\ And then reclaim it

1500 .Setup

1510 LDY #0

1520 .SetupLp

1530 LDA load%,Y:STA run%,Y:INY:BNE SetupLp :\ Copy code to main memory

1540 LDA USERV+1:LDX OldUSERV+1 :\ Claim USERV

1550 STX USERV+1:STA OldUSERV+1

1560 LDA USERV+0:LDX OldUSERV+0

1570 STX USERV+0:STA OldUSERV+0

1580 .SetupExit

1590 PLP:RTS :\ Exit

1600 :

1610 ]NEXT

1620 PRINT "*SAVE OswFFv2 ";~mcode%;" ";~O%;" ";~exec%OR&FFFF0000;" ";~load%