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Flight: hyp

[BBC Micro disc version, Docked]

Name: hyp [Show more] Type: Subroutine Category: Flight Summary: Start the hyperspace process
Context: See this subroutine in context in the source code Variations: See code variations for this subroutine in the different versions References: This subroutine is called as follows: * TTX110 calls via TTX111

Called when "H" or CTRL-H is pressed during flight. Checks the following: * We are in space * We are not already in a hyperspace countdown If CTRL is being held down, we jump to Ghy to engage the galactic hyperdrive, otherwise we check that: * The selected system is not the current system * We have enough fuel to make the jump and if all the pre-jump checks are passed, we print the destination on-screen and start the countdown.
Other entry points: TTX111 Used to rejoin this routine from the call to TTX110
.hyp LDA QQ22+1 \ Fetch QQ22+1, which contains the number that's shown \ on-screen during hyperspace countdown ORA QQ12 \ If we are docked (QQ12 = &FF) or there is already a BNE zZ+1 \ countdown in progress, then return from the subroutine \ using a tail call (as zZ+1 contains an RTS), as we \ can't hyperspace when docked, or there is already a \ countdown in progress JSR CTRL \ Scan the keyboard to see if CTRL is currently pressed BMI Ghy \ If it is, then the galactic hyperdrive has been \ activated, so jump to Ghy to process it LDA QQ11 \ If the current view is 0 (i.e. the space view) then BEQ TTX110 \ jump to TTX110, which calls TT111 to set the current \ system to the nearest system to (QQ9, QQ10), and jumps \ back into this routine at TTX111 below AND #%11000000 \ If neither bit 6 nor 7 of the view type is set - so BEQ zZ+1 \ this is neither the Short-range or Long-range Chart - \ then return from the subroutine (as zZ+1 contains an \ RTS) JSR hm \ This is a chart view, so call hm to redraw the chart \ crosshairs .TTX111 \ If we get here then the current view is either the \ space view or a chart LDA QQ8 \ If both bytes of the distance to the selected system ORA QQ8+1 \ in QQ8 are zero, return from the subroutine (as zZ+1 BEQ zZ+1 \ contains an RTS), as the selected system is the \ current system LDA #7 \ Move the text cursor to column 7, row 22 (in the STA XC \ middle of the bottom text row) LDA #22 STA YC LDA #0 \ Set QQ17 = 0 to switch to ALL CAPS STA QQ17 LDA #189 \ Print recursive token 29 ("HYPERSPACE ") JSR TT27 LDA QQ8+1 \ If the high byte of the distance to the selected BNE TT147 \ system in QQ8 is > 0, then it is definitely too far to \ jump (as our maximum range is 7.0 light years, or a \ value of 70 in QQ8(1 0)), so jump to TT147 to print \ "RANGE?" and return from the subroutine using a tail \ call LDA QQ14 \ Fetch our current fuel level from Q114 into A CMP QQ8 \ If our fuel reserves are less than the distance to the BCC TT147 \ selected system, then we don't have enough fuel for \ this jump, so jump to TT147 to print "RANGE?" and \ return from the subroutine using a tail call LDA #'-' \ Print a hyphen JSR TT27 JSR cpl \ Call cpl to print the name of the selected system \ Fall through into wW to start the hyperspace countdown