HOW to gernerate frequecy from 1 Hz to 200 Hz using timer as interrupt in 89S52

[bondhwal]

HI

I want to write routine like this
;==================================

; Crystal Frequency = 24MHz
;
; mode setting for timer
MOV TMOD,#0H ; mode 0, 13-bit timer
MOV SAV_TH1,#254;
MOV SAV_TL1,#27
MOV TL1,SAV_TL1
MOV TH1,SAV_TH1


TIMER1_ISR:
PUSH ACC ; 1uS
PUSH PSW ; 1uS
NOP ;.5uS ;
CLR TR1 ; .5uS ;timer interrupt
MOV TL1,SAV_TL1 ;1uS
MOV TH1,SAV_TH1 ;1uS
NOP ;.5uS
SETB TR1 ; .5uS
MOV PSW,#018H ;1uS
JB OUTPUT,CLR_OUTPUT ;1uS
CJNE R7,#00,RET_T11 ;1uS
MOV R7,PWM_MULTP2 ;1uS
SETB OUTPUT ;.5uS
NOP ;.5uS
JMP RET_T1 ;1uS
RET_T11: NOP ;.5uS
DEC R7 ;.5uS
RET_T1:
POP PSW ;1 uS
POP ACC ;1 uS
RETI ;
CLR_OUTPUT:
CJNE R7,#00,RET_T11 ;1uS
DJNZ R6,RET_T1 ;1uS
MOV R6,#2 ;1uS
DJNZ R5,RET_T1 ;1uS
MOV R5,#235 ;1uS
MOV R7,PWM_MULTP1 ;1uS
NOP ;.5uS
CLR OUTPUT ;.5uS
JMP RET_T1 ;1uS
================================

I need help in making a formula to generate frequency from 1Hz to 200 Hz with above asm code.
Pls reply.