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Elite on the BBC Micro

Dashboard: WPSHPS (Cassette version)

Name: WPSHPS [View in context] Type: Subroutine [Compare versions] Category: Dashboard Summary: Clear the scanner, reset the ball line and sun line heaps
Remove all ships from the scanner, reset the sun line heap at LSO, and reset the ball line heap at LSX2 and LSY2.
.WPSHPS LDX #0 \ Set up a counter in X to work our way through all the \ ship slots in FRIN .WSL1 LDA FRIN,X \ Fetch the ship type in slot X BEQ WS2 \ If the slot contains 0 then it is empty and we have \ checked all the slots (as they are always shuffled \ down in the main loop to close up and gaps), so jump \ to WS2 as we are done BMI WS1 \ If the slot contains a ship type with bit 7 set, then \ it contains the planet or the sun, so jump down to WS1 \ to skip this slot, as the planet and sun don't appear \ on the scanner STA TYPE \ Store the ship type in TYPE JSR GINF \ Call GINF to get the address of the data block for \ ship slot X and store it in INF LDY #31 \ We now want to copy the first 32 bytes from the ship's \ data block into INWK, so set a counter in Y .WSL2 LDA (INF),Y \ Copy the Y-th byte from the data block pointed to by STA INWK,Y \ INF into the Y-th byte of INWK workspace DEY \ Decrement the counter to point at the next byte BPL WSL2 \ Loop back to WSL2 until we have copied all 32 bytes STX XSAV \ Store the ship slot number in XSAV while we call SCAN JSR SCAN \ Call SCAN to plot this ship on the scanner, which will \ remove it as it's plotted with EOR logic LDX XSAV \ Restore the ship slot number from XSAV into X LDY #31 \ Clear bits 3, 4 and 6 in the ship's byte #31, which LDA (INF),Y \ stops drawing the ship on-screen (bit 3), hides it AND #%10100111 \ from the scanner (bit 4) and stops any lasers firing STA (INF),Y \ at it (bit 6) .WS1 INX \ Increment X to point to the next ship slot BNE WSL1 \ Loop back up to process the next slot (this BNE is \ effectively a JMP as X will never be zero) .WS2 LDX #&FF \ Set LSX2 = LSY2 = &FF to clear the ball line heap STX LSX2 STX LSY2 \ Fall through into FLFLLS to reset the LSO block