FastLdir

                device zxspectrum48

                org #8000
start:
                jr $            ; to stop Z80 CPU here

                LD HL,0         ; rom address
                LD DE,#4000     ; screen address
                LD BC,#0001     ; bytes count


@klFastLDIR:    xor a           ; 0
                sub c           ; 0 - count
                add a           ; 2 * (0 - count)
                and %01111110   ; = 126,  for:  MOD(2*(0-count), 64*2)
                ld  (VectorJPAddr+1), a ; patch jump address
VectorJPAddr:   jp  klLDI64     ; jump at rest LDI
                ALIGN   256
@klLDI64:       DUP 64
                ldi             ; 64 * LDI instructions
                EDUP
                jp  pe, klLDI64 ; loop LDI, simulate LDIR
                ret

                savesna "FastLdir.sna",start