.ECBLB LDA #8*14 \ The E.C.M. bulb is in character block number 14 with STA SC \ each character taking 8 bytes, so this sets the low \ byte of the screen address of the character block we \ want to draw to LDA #&7A \ Set the high byte of SC(1 0) to &7A, as the bulbs are STA SC+1 \ both in the character row from &7A00 to &7BFF, and the \ E.C.M. bulb is in the left half, which is from &7A00 \ to &7AFF LDY #15 \ Now to poke the bulb bitmap into screen memory, and \ there are two character blocks' worth, each with eight \ lines of one byte, so set a counter in Y for 16 bytes .BULL2 LDA ECBT,Y \ Fetch the Y-th byte of the bulb bitmap EOR (SC),Y \ EOR the byte with the current contents of screen \ memory, so drawing the bulb when it is already \ on-screen will erase it STA (SC),Y \ Store the Y-th byte of the bulb bitmap in screen \ memory DEY \ Decrement the loop counter BPL BULL2 \ Loop back to poke the next byte until we have done \ all 16 bytes across two character blocks JMP PUTBACK \ Jump to PUTBACK to restore the USOSWRCH handler and \ return from the subroutine using a tail callName: ECBLB [View in context] Type: Subroutine Category: Dashboard Summary: Implement the #DOBULB 255 command (draw the E.C.M. indicator bulb)
This routine is run when the parasite sends a #DOBULB 255 command. It draws (or erases) the E.C.M. indicator bulb ("E") on the dashboard.
Label BULL2 is local to this routine
The character bitmap for the E.C.M. indicator bulb
Reset the OSWRCH vector in WRCHV to point to USOSWRCH