LED blink rate controlled by two switches

Idea

The LED at P1.1 is toggled forever. The half-period is R2 x 10 ms. Switch S1 (P2.1) decreases R2 (faster blink) and switch S2 (P2.2) increases R2 (slower blink). Switches are active low (pressed = 0, with pull-ups). Limits keep R2 within 1 to 255.

 Start --> R2 = 20 --> toggle P1.1 --> wait R2 x 10 ms
            ^                              |
            |   S2 pressed & R2<255: R2++ |
            +--  S1 pressed & R2>1 : R2-- <+

Program

        ORG 0000H
        MOV P2,#0FFH       ; P2 as input (write 1s), switches active low
        MOV R2,#20         ; half-period = 20 x 10 ms = 200 ms
MAIN:   CPL P1.1           ; toggle LED
        MOV A,R2
        MOV R3,A           ; R3 = number of 10 ms units
WAIT:   ACALL DELAY10      ; 10 ms
        DJNZ R3,WAIT
        JB P2.1,CHK2       ; P2.1 = 1 -> "faster" switch not pressed
        CJNE R2,#1,DECR    ; already at minimum (fastest)?
        SJMP CHK2
DECR:   DEC R2             ; shorter delay = faster blinking
CHK2:   JB P2.2,MAIN       ; P2.2 = 1 -> "slower" switch not pressed
        CJNE R2,#0FFH,INCR ; already at maximum (slowest)?
        SJMP MAIN
INCR:   INC R2             ; longer delay = slower blinking
        SJMP MAIN

DELAY10: MOV R6,#20        ; about 10 ms at 12 MHz
L1:     MOV R7,#248
L2:     DJNZ R7,L2
        DJNZ R6,L1
        RET
        END

Explanation:

• MOV P2,#0FFH makes P2 an input port.
• CPL P1.1 toggles the LED; the delay is R2 repetitions of DELAY10 (10 ms), so the half-period is R2 x 10 ms (200 ms initially, 2.5 Hz blinking).
• JB P2.1,CHK2 skips if S1 is not pressed; if pressed and R2 is not yet 1, DEC R2 makes the delay shorter, so the blink is faster.
• JB P2.2,MAIN skips if S2 is not pressed; if pressed and R2 is not yet 255, INC R2 makes the blink slower.
• In simulation, holding S1 reduced the half-period 0.20 s to 0.19 s to 0.18 s per toggle and S2 raised it again.