The EOR operator
The instruction EOR exclusive or will return a true value 1 if one, and only one, of the bits in the pair being tested is a 1. The following turth table is for the EOR operator. The EOR instruction is often used for comparing bytes to determine if they are identical, since if any bit in two bytes is different, the result of a comparison will be non-zero. Here is an illustration of that comparison. 1011 0110 1011 0110 EOR 10110110 But EOR 10110111 In Example 1, the bytes being compared are...
An Example Of Coarse Scrolling
110 SDLSTL 0230 120 SDLSTH 0231 130 140 C L R0 02C4 GS COLOR REGISTERS 230 LINE1 .SBYTE PRESENTING 240 LINE2 .SBYTE 250 .SBYTE the big program 260 .SBYTE 270 LINE3 .SBYTE By You 280 .SBYTE r Name 290 LINE4 .SBYTE PLEASE STAND BY 300 520 LDA COLOR3 530 STA COLOR1 540 LDA C0L0R4 550 STA C0L0R2 560 570 LDA 0 580 STA SDMCTL 590 LDA HLIST amp 255 600 STA SDLSTL 610 LDA HLIST 256 620 STA SDLSTH 630 LDA 22 640 STA SDMCTL 650 680 LDA 40 690 STA TCKPTR 700 JSR TCKSET 710 1 030 TCKSET 1040 LDA LINE2 amp...
The MEMLO Pointer
MEMLO is also a 16-bit value, but is stored in memory addresses 2E7 and 2E8 of your computer or 743 and 744 in decimal notation . When you turn your computer on, without a cartridge or a disk in it, your computer's MEMLO pointer always contains the lowest free address in RAM, the lowest address at which user written programs can begin. That means, that when you turn your computer on, MEMLO and LOMEM contain exactly the same address, the lowest free address in RAM. That address is also the...