Retrocomputing

System definitions

The sysdefs file contains the characteristics of the specific architecture, such as the definition of the MMU, devices etc.

         opt  -l
         ttl System Type Definitions for the Dragon 128
         page
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 ifeq CPUType-DRG128
************************************************************ * * Dynamic Address Translator Definitions * *************** * * Note that DAT.BlCt is also understood by AllProc and * Chain (in OS9-P2) to be the number of blocks available * to each task. If less than 64k is available, these * routines must be modified to put DAT.Free in the * blocks that can be allocated, and the required values * into the other blocks, (eg the I/O block), to complete * the DAT image. * DAT.BlCt equ 16 D.A.T. blocks/address space available * *************** DAT.BlUs equ 15 blocks available for RAM in address space DAT.GBlk equ DAT.BlCt*2 number of graphics blocks DAT.Blsz equ $1000 D.A.T. block size in bytes DAT.ImSz equ DAT.BlCt*2 D.A.T. Image size *************** * * DAT.Addr calculates a mask for the top bits of the * logical address that are mapped by the MMU DAT.Addr equ -(DAT.BlSz/256) D.A.T. MSB Address bits * *************** *************** * * This version is assuming that the MMU access * and operate keys are the same register DAT.Task equ $FCC0 Task register address DAT.TMsk equ $0F bits of register for task number DAT.Uniq equ 1 bits of DAT Task register are not used for other things * *************** DAT.TkCt equ 16 task maps in the MMU DAT.Regs equ $FE00 DAT RAM base address *************** * * One block number must be guaranteed never to * contain memory, (ROM or RAM). That block number * is used by OS9 in the block map and DAT images * to indicate an unallocated logical block DAT.Free equ $C0 * *************** DAT.BlMx equ $FF maximum block number DAT.BMSz equ $100 Block Map size (one byte per block) DAT.WrPr equ 0 no Block Write Protect bit DAT.WrEn equ 0 no Block Write Enable bit *************** * * A task number of 0 is used to indicate * 'no DAT task map allocated'. Therefore * no actual DAT task number can be 0. The easiest * thing to do is to set a bit in SysTask that * has no effect on the DAT. If the DAT register * cares about all 8 bits, then DATInit, SvcRet, * PassSWI, LDABX, STABX, LDBBX, Mover00, SetDAT00, * and Switch, (all at the end of OS9-P1), must be * altered to ensure that the bits are correctly * set * For the Dragon 128, the chosen value of SysTask * includes fixed outputs, LMap and DPIRQ. SysTask equ $80 System Task number * *************** IOBlock equ $FF The block number for the I/O *************** * * OS9-P1 ColdStart initially sets up the system map * with RAM block 0 at $0000, a ROMBlock at $E000, * and the IOBlock at $F000. ROMBlock equ $FE ROM block mapped in on ColdStart at $E000 ROMCount equ 1 number of blocks of ROM to so map in RAMCount equ 1 initial blocks of RAM * *************** ROMCheck equ Limited check only top 64k for ROM RAMCheck equ BlockTyp check only first bytes of RAM blocks LastRAM equ $BF maximum RAM block number *************** * * If the I/O is addressed whenever the top * address lines of the micro, (ie the logical * bus), take a certain value, rather than being * addressed through the DAT, then MappedIO must * be set false (0) MappedIO equ 1 * *************** ********** * Several system modules expect to be * able to abort the startup procedure * and retry, by jumping through a ROM * vector (usually the reset vector). * D$REBOOT equ $FFEE use an unused vector * ********** ClocType set VSYNC TickSec set 50 ticks per second (50 for UK, 60 for USA) Cx2Int set 1 CA2 (CB2) interrupt input FPort set $FCE0 floppy disk controller HPort set $FD00 hard disk controller DrvCnt set 4 four drives DPort set FPort A.T1 set $FC40 serial port address A.T.Init set $15 default ACIA initialisation byte A.P set $FC20 address of parallel printer port A.P1 set A.T1 address of serial printer port A.KBD set A.P+2 keyboard port address A.KLoad set A.KBD port whose control reg has keyboard LOAD A.GCon equ DAT.Task+2 graphics control port A.Cont equ DAT.Task+1 control reg with CONTROL bit A.Clock set A.GCon clock VSYNC interrupts come in on CB2 A.Crtc equ $FC80 address of 6845 CRTC A.ColMap equ $FCA0 address of colour map A.Mouse equ $FC24 mouse and disk select A.DskSel equ A.Mouse disk select port A.Beeper equ A.DskSel+2 port with beeper on it A.ChrSet equ A.Beeper port with 'character set select' A.Baud equ A.Beeper port with baud rate setting B.DPHalt equ $80 DMA processor HALT bit in disk Select port B.DPNMI equ $80 DMA processor interrupt bit in DAT Task reg B.Bell equ 1 beeper bit B.Contrl equ $08 CA2 is CONTROL bit B.ChrSet equ $40 character set select bit B.MPHalt equ 2 Main Processor HALT bit B.PDir equ $80 printer port buffer direction bit
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