Having the lookup table in xdata memory turns out to be shorter than having it in pdata memory:)

#include <8052.h>

static unsigned char ms_tenth_countdown;

// dynamically setup table.
// Indexed top down.
// setup this table glitchlessly (IRQ save).
// (located absolutely at the start of a 256 byte block)
unsigned char __xdata __at(0x0000) table_P2_over_time[200 + 1];

void Timer0_ISR (void) interrupt 1 {

    // assuming P2 is only used for servos.
    P2 = table_P2_over_time [ ms_tenth_countdown ];

    if (!--ms_tenth_countdown)
        ms_tenth_countdown = 200;

    TF0 = 0;
}

void main(void){}

 

gives:

; File Created by SDCC : free open source ANSI-C Compiler
; Version 2.9.5 #5614 (Jan  4 2010) (UNIX)

   0000                     370 _Timer0_ISR:
   0000 C0 E0               379         push    acc
   0002 C0 82               380         push    dpl
   0004 C0 83               381         push    dph
                            382 ;       servo_lookup.c:14: P2 = table_P2_over_time [ ms_tenth_countdown ];

   0006 85*00 82            383         mov     dpl,_ms_tenth_countdown
   0009 75 83 00            384         mov     dph,#(_table_P2_over_time >> 8)
   000C E0                  385         movx    a,@dptr
   000D F5 A0               386         mov     _P2,a
                            387 ;       servo_lookup.c:16: if (!--ms_tenth_countdown)
   000F D5*00 03            388         djnz    _ms_tenth_countdown,00102$
                            389 ;       servo_lookup.c:17: ms_tenth_countdown = 200;
   0012 75*00 C8            390         mov     _ms_tenth_countdown,#0xC8
   0015                     391 00102$:
                            392 ;       servo_lookup.c:19: TF0 = 0;
   0015 C2 8D               393         clr     _TF0
   0017 D0 83               394         pop     dph
   0019 D0 82               395         pop     dpl
   001B D0 E0               396         pop     acc
   001D 32                  397         reti

 

guess that's hard to beat!)