Mountain Computer ROMPlus+ Operating Manual

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Chapter 3ADVANCED PROGRAMMERS INFORMATIONBit 2-0: These bits select the ROM socket to be enabled.Bit two is the most significant bit of thevalue. If the value=O, then none of the ROMsare enabled. If set from 1 t~6, the correspondingROM is enabled. The value should neverequal 7.A read to the control word is used to check the status of theRAM, find the currently enabled ROM socket number, or to sensethe value of the two TTL inputs. The function of the particularbits are described below.control wordBit 7:Bit 6 :Bit 5 :Bit 4 :Bit 3 :Bit 2-0 :This bit reads the status of RAM. If equal to"0", then RAM is deactivated. If equal to "1",then RAM is active.Unused.TTL input from pin 4.TTL input from pin 1.Unused.These bits indicate which Rom socket is currentlyenabled. The value is determined the sameway as the bits 2-0 of the written control word.We next examine several programming examples of control word use.First, if we wish to activate ROMPLUS+ and select ROM socketnumber one, we use these machine language instructions:LDA #$89STA $C080,X:RAM active, board active, ROM #1:Write control wordIn that example, and in the examples to follow, we assume thatthe X register contains the slot number (1-7) multiplied by 16.This is the standard convention for slot independent 1/0 on AppleII.To do the same thing in BASIC, we use a statement like this:POKE -16256+16*SLOT,1373-2
Chapter 3ADVANCED PROGRAMMERS INFORMATIONNow suppose you wish to activate ROMPLUS+, deactivate the RAM,and select ROM #5. You would do one of the following:LDA #$OD:Deactivate RAM, activate ROMPLUS+, selectROM #5.STA $COSO,X :Write control wordor POKE -16256+16*SLOT,13If you wish to toggle the state of the RAM (i.e., turn off whenit is on and turn on when it is off), you would use this code:LDAEORORASTA$COSO,X :Read control word#$SO#$SO$COSO,X :Write control wordFrom BASIC, use these statements:S=(PEEK(-16256+16*SLOT)+12S)MOD 256IF S MOD 16
Page 3 and 4: Table of ContentsiiiChapter 1INTROD
Page 5: INST ALL A TIONTo install ROMPLUS+
Page 9 and 10: Chapter 2USING ROMPLUS+This chapter
Page 11 and 12: Chapter 2USING ROMPLUS+CTRL-SHIFT-M
Page 13: Chapter 3ADVANCED PROGRAMMER'S INFO
Page 17 and 18: Chapter 3ADVANCED PROGRAMMERS INFOR
Page 19 and 20: Chapter 3ADVANCED PROGRAMMERS INFOR
Page 21: Chapter 4REFERENCEa ROM socket. ROM
Page 24 and 25: Appendix ACONTROL ROM SOURCE LISTIN
Page 26 and 27: Appendix ACONTROL ROM SOURCE LISTIN
Page 28: Appendix ACONTROL ROM SOURCE LISTIN

Mountain Computer ROMPlus+ Operating Manual

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