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Elite on the BBC Micro

Keyboard: TT102 (Master version)

Name: TT102 [View in context] Type: Subroutine [Compare versions] Category: Keyboard Summary: Process function key, save, hyperspace and chart key presses
Process function key presses, plus "@" (save commander), "H" (hyperspace), "D" (show distance to system) and "O" (move chart cursor back to current system). We can also pass cursor position deltas in X and Y to indicate that the cursor keys or joystick have been used (i.e. the values that are returned by routine TT17). This routine also checks for the "F" key press (search for a system), which applies to enhanced versions only. Arguments: A The internal key number of the key pressed (see p.142 of the Advanced User Guide for a list of internal key numbers) X The amount to move the crosshairs in the x-axis Y The amount to move the crosshairs in the y-axis Other entry points: T95 Print the distance to the selected system
.TT102 CMP #f8 \ If red key f8 was pressed, jump to STATUS to show the BNE P%+5 \ Status Mode screen, returning from the subroutine JMP STATUS \ using a tail call CMP #f4 \ If red key f4 was pressed, jump to TT22 to show the BNE P%+5 \ Long-range Chart, returning from the subroutine using JMP TT22 \ a tail call CMP #f5 \ If red key f5 was pressed, jump to TT23 to show the BNE P%+5 \ Short-range Chart, returning from the subroutine using JMP TT23 \ a tail call CMP #f6 \ If red key f6 was pressed, call TT111 to select the BNE TT92 \ system nearest to galactic coordinates (QQ9, QQ10) JSR TT111 \ (the location of the chart crosshairs) and set ZZ to JMP TT25 \ the system number, and then jump to TT25 to show the \ Data on System screen (along with an extended system \ description for the system in ZZ if we're docked), \ returning from the subroutine using a tail call .TT92 CMP #f9 \ If red key f9 was pressed, jump to TT213 to show the BNE P%+5 \ Inventory screen, returning from the subroutine JMP TT213 \ using a tail call CMP #f7 \ If red key f7 was pressed, jump to TT167 to show the BNE P%+5 \ Market Price screen, returning from the subroutine JMP TT167 \ using a tail call CMP #f0 \ If red key f0 was pressed, jump to TT110 to launch our BNE fvw \ ship (if docked), returning from the subroutine using JMP TT110 \ a tail call .fvw BIT QQ12 \ If bit 7 of QQ12 is clear (i.e. we are not docked, but BPL INSP \ in space), jump to INSP to skip the following checks \ for f1-f3 and "@" (save commander file) key presses CMP #f3 \ If red key f3 was pressed, jump to EQSHP to show the BNE P%+5 \ Equip Ship screen, returning from the subroutine using JMP EQSHP \ a tail call CMP #f1 \ If red key f1 was pressed, jump to TT219 to show the BNE P%+5 \ Buy Cargo screen, returning from the subroutine using JMP TT219 \ a tail call CMP #&40 \ If "@" was not pressed, skip to nosave BNE nosave JSR SVE \ "@" was pressed, so call SVE to show the disc access \ menu BCC P%+5 \ If the C flag was set by SVE, then we loaded a new JMP QU5 \ commander file, so jump to QU5 to restart the game \ with the newly loaded commander JMP BAY \ Otherwise the C flag was clear, so jump to BAY to go \ to the docking bay (i.e. show the Status Mode screen) .nosave CMP #f2 \ If red key f2 was pressed, jump to TT208 to show the BNE LABEL_3 \ Sell Cargo screen, returning from the subroutine using JMP TT208 \ a tail call .INSP CMP #f1 \ If red key f1 was pressed, jump to BVIEW BEQ BVIEW CMP #f2 \ If red key f2 was pressed, jump to LVIEW BEQ LVIEW CMP #f3 \ If red key f3 was not pressed, jump to LABEL_3 to keep BNE LABEL_3 \ checking for which key was pressed LDX #3 \ Red key f3 was pressed, so set the view number in X to \ 3 for the right view EQUB &2C \ Skip the next instruction by turning it into \ &2C &A2 &02, or BIT &02A2, which does nothing apart \ from affect the flags .LVIEW LDX #2 \ If we jump to here, red key f2 was pressed, so set the \ view number in X to 2 for the left view EQUB &2C \ Skip the next instruction by turning it into \ &2C &A2 &01, or BIT &02A2, which does nothing apart \ from affect the flags .BVIEW LDX #1 \ If we jump to here, red key f1 was pressed, so set the \ view number in X to 1 for the rear view JMP LOOK1 \ Jump to LOOK1 to switch to view X (rear, left or \ right), returning from the subroutine using a tail \ call .LABEL_3 LDA KL \ If "H" was not pressed, jump to NWDAV5 to skip the CMP #'H' \ following BNE NWDAV5 JMP hyp \ Jump to hyp to do a hyperspace jump (if we are in \ space), returning from the subroutine using a tail \ call .NWDAV5 CMP #&44 \ If "D" was pressed, jump to T95 to print the distance BEQ T95 \ to a system (if we are in one of the chart screens) CMP #&46 \ If "F" was not pressed, jump down to HME1, otherwise BNE HME1 \ keep going to process searching for systems LDA QQ12 \ If QQ12 = 0 (we are not docked), we can't search for BEQ t95 \ systems, so return from the subroutine (as t95 \ contains an RTS) LDA QQ11 \ If the current view is a chart (QQ11 = 64 or 128), AND #%11000000 \ keep going, otherwise return from the subroutine (as BEQ t95 \ t95 contains an RTS) JMP HME2 \ Jump to HME2 to let us search for a system, returning \ from the subroutine using a tail call .HME1 STA T1 \ Store A (the key that's been pressed) in T1 LDA QQ11 \ If the current view is a chart (QQ11 = 64 or 128), AND #%11000000 \ keep going, otherwise jump down to TT107 to skip the BEQ TT107 \ following LDA QQ22+1 \ If the on-screen hyperspace counter is non-zero, BNE TT107 \ then we are already counting down, so jump to TT107 \ to skip the following LDA T1 \ Restore the original value of A (the key that's been \ pressed) from T1 CMP #&4F \ If "O" was pressed, do the following three jumps, BNE ee2 \ otherwise skip to ee2 to continue JSR TT103 \ Draw small crosshairs at coordinates (QQ9, QQ10), \ which will erase the crosshairs currently there JSR ping \ Set the target system to the current system (which \ will move the location in (QQ9, QQ10) to the current \ home system JMP TT103 \ Draw small crosshairs at coordinates (QQ9, QQ10), \ which will draw the crosshairs at our current home \ system, and return from the subroutine using a tail \ call .ee2 JSR TT16 \ Call TT16 to move the crosshairs by the amount in X \ and Y, which were passed to this subroutine as \ arguments .TT107 LDA QQ22+1 \ If the on-screen hyperspace counter is zero, return BEQ t95 \ from the subroutine (as t95 contains an RTS), as we \ are not currently counting down to a hyperspace jump DEC QQ22 \ Decrement the internal hyperspace counter BNE t95 \ If the internal hyperspace counter is still non-zero, \ then we are still counting down, so return from the \ subroutine (as t95 contains an RTS) \ If we get here then the internal hyperspace counter \ has just reached zero and it wasn't zero before, so \ we need to reduce the on-screen counter and update \ the screen. We do this by first printing the next \ number in the countdown sequence, and then printing \ the old number, which will erase the old number \ and display the new one because printing uses EOR \ logic LDX QQ22+1 \ Set X = the on-screen hyperspace counter - 1 DEX \ (i.e. the next number in the sequence) JSR ee3 \ Print the 8-bit number in X at text location (0, 1) LDA #5 \ Reset the internal hyperspace counter to 5 STA QQ22 LDX QQ22+1 \ Set X = the on-screen hyperspace counter (i.e. the \ current number in the sequence, which is already \ shown on-screen) JSR ee3 \ Print the 8-bit number in X at text location (0, 1), \ i.e. print the hyperspace countdown in the top-left \ corner DEC QQ22+1 \ Decrement the on-screen hyperspace countdown BNE t95 \ If the countdown is not yet at zero, return from the \ subroutine (as t95 contains an RTS) JMP TT18 \ Otherwise the countdown has finished, so jump to TT18 \ to do a hyperspace jump, returning from the subroutine \ using a tail call .t95 RTS \ Return from the subroutine .T95 \ If we get here, "D" was pressed, so we need to show \ the distance to the selected system (if we are in a \ chart view) LDA QQ11 \ If the current view is a chart (QQ11 = 64 or 128), AND #%11000000 \ keep going, otherwise return from the subroutine (as BEQ t95 \ t95 contains an RTS) JSR hm \ Call hm to move the crosshairs to the target system \ in (QQ9, QQ10), returning with A = 0 JSR cpl \ Print control code 3 (the selected system name) LDA #%10000000 \ Set bit 7 of QQ17 to switch to Sentence Case, with the STA QQ17 \ next letter in capitals LDA #12 \ Print a line feed to move the text cursor down a line JSR TT26 JMP TT146 \ Print the distance to the selected system and return \ from the subroutine using a tail call