Z80 routine to clamp value in HL to -0x100 to +0x100 range

limitHlValue.asm

LimitHlValue:
  ; In: HL = value to be clamped to -0x100 .. +0x100
  ; Out: HL = clamped value
  ; Uses: A + flags
  ; (this is not mathematically correct, values 0x7F?? clamp to -0x100, for performance reasons)
    ld  a,h
    inc a
    sra a           ; will be 0 for -256..+255 (+256 will get "clamped")
    ret z
    ld  hl,0x100
    ret p           ; if A was positive, clamp to 0x100
    ld  h,high -0x100   ; -0x100 = 0xFF00, L is already zero
    ; "ld h,0xFF" if your assembler doesn't have "high" (sjasmplus has)
    ret