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Elite on the BBC Micro

Keyboard: TT102 [Elite-A, Flight]

Name: TT102 [Show more] Type: Subroutine Category: Keyboard Summary: Process function key, save key, hyperspace and chart key presses and update the hyperspace counter
Context: See this subroutine in context in the source code References: This subroutine is called as follows: * Main game loop (Part 6 of 6) calls TT102 * Main game loop (Part 3 of 6) calls entry point BAD * TT110 calls entry point BAD * Main game loop (Part 6 of 6) calls entry point TT107

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). 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: BAD Work out how bad we are from the amount of contraband in our hold T95 Print the distance to the selected system TT107 Progress the countdown of the hyperspace counter
.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 CMP #f1 \ If the key pressed is < red key f1 or > red key f3, BCC LABEL_3 \ jump to LABEL_3 (so only do the following if the key CMP #f3+1 \ pressed is f1, f2 or f3) BCS LABEL_3 AND #3 \ If we get here then we are either in space, or we are TAX \ docked and none of f1-f3 were pressed, so we can now JMP LOOK1 \ process f1-f3 with their in-flight functions, i.e. \ switching space views \ \ A will contain &71, &72 or &73 (for f1, f2 or f3), so \ set X to the last digit (1, 2 or 3) and jump to LOOK1 \ to switch to view X (rear, left or right), returning \ from the subroutine using a tail call .LABEL_3 CMP #&54 \ If "H" was pressed, jump to hyp to do a hyperspace BNE P%+5 \ jump (if we are in space), returning from the JMP hyp \ subroutine using a tail call CMP #&32 \ 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) \ --- Mod: Code added for Elite-A: --------------------> CMP #&43 \ If "F" was not pressed, jump down to HME1, otherwise BNE HME1 \ keep going to toggle the compass display LDA finder \ Set the value of A to finder, which determines whether \ the compass is configured to show the sun or the \ planet EOR #NI% \ The value of finder is 0 (show the planet) or NI% \ (show the sun), so this toggles the value between the \ two STA finder \ Store the toggled value in finder JMP WSCAN \ Jump to WSCAN to wait for the vertical sync and return \ from the subroutine using a tail call .HME1 \ --- End of added code -------------------------------> STA T1 \ Store A (the key that's been pressed) in T1 \ --- Mod: Original Acornsoft code removed: -----------> \ 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 \ --- And replaced by: --------------------------------> 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 and move on to updating the hyperspace \ counter \ --- End of replacement ------------------------------> LDA T1 \ Restore the original value of A (the key that's been \ pressed) from T1 \ --- Mod: Original Acornsoft code removed: -----------> \ CMP #&36 \ If "O" was pressed, do the following three jumps, \ BNE ee2 \ otherwise skip to ee2 to continue \ --- And replaced by: --------------------------------> CMP #&36 \ If "O" was pressed, do the following three jumps, BNE not_home \ otherwise skip to not_home to continue checking key \ presses \ --- End of replacement ------------------------------> 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 \ --- Mod: Original Acornsoft code removed: -----------> \ JSR TT103 \ Draw small crosshairs at coordinates (QQ9, QQ10), \ \ which will draw the crosshairs at our current home \ \ system \ --- And replaced by: --------------------------------> 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 \ --- End of replacement ------------------------------> .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 \ --- Mod: Code added for Elite-A: --------------------> .BAD LDA QQ20+3 \ Set A to the number of tonnes of slaves in the hold CLC \ Clear the C flag so we can do addition without the \ C flag affecting the result ADC QQ20+6 \ Add the number of tonnes of narcotics in the hold ASL A \ Double the result and add the number of tonnes of ADC QQ20+10 \ firearms in the hold \ --- End of added code -------------------------------> .t95 RTS \ Return from the subroutine \ --- Mod: Code added for Elite-A: --------------------> .not_home CMP #&21 \ If "W" was pressed, continue on to move the crosshairs BNE ee2 \ to the special cargo destination, otherwise skip to \ ee2 to continue LDA cmdr_cour \ If there is no special cargo delivery mission in ORA cmdr_cour+1 \ progress, then the mission timer in cmdr_cour(1 0) BEQ ee2 \ will be zero, so skip to ee2 to continue JSR TT103 \ Draw small crosshairs at coordinates (QQ9, QQ10), \ which will erase the crosshairs currently there LDA cmdr_courx \ Set the galactic coordinates in (QQ9, QQ10) to the STA QQ9 \ current special cargo delivery destination in LDA cmdr_coury \ (cmdr_courx, cmdr_coury) STA QQ10 JSR TT103 \ Draw small crosshairs at coordinates (QQ9, QQ10), \ which will draw the crosshairs at our current home \ system \ --- End of added code -------------------------------> .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 STA QQ17 \ Set QQ17 = 0 to switch to ALL CAPS JSR cpl \ Print control code 3 (the selected system name) \ --- Mod: Original Acornsoft code removed: -----------> \ LDA #%10000000 \ Set bit 7 of QQ17 to switch to Sentence Case, with the \ STA QQ17 \ next letter in capitals \ --- And replaced by: --------------------------------> JSR vdu_80 \ Call vdu_80 to switch to Sentence Case, with the next \ letter in capitals \ --- End of replacement ------------------------------> LDA #1 \ Move the text cursor to column 1 and down one line STA XC \ (in other words, to the start of the next line) INC YC JMP TT146 \ Print the distance to the selected system and return \ from the subroutine using a tail call