PIC timing

Okay, I was curious about the actual speed my controller
is running at, so I ran the following loop on it. If I'm not mistaken,
I've set OSCCON to 8MHz, so at 4 clock/instruction I should see
0.5 uS pulses. My scope on RB4 shows pulses 5uS wide!

I'm out by a factor of 10. What have I not taken into account?


#include <p16F690.inc>
__config (_INTRC_OSC_NOCLKOUT & _WDT_OFF & _PWRTE_OFF & _MCLRE_OFF &
_CP_OFF & _BOR_OFF & _IESO_OFF & _FCMEN_OFF)

Org 0
goto Start
Org 4
goto ISR
ISR
retfie

Start movlw 0x71 ;b'01110001'
BANKSEL OSCCON
movwf OSCCON

; initialize any register that might affect I/O
BANKSEL IOCB
clrf IOCB
clrf WPUB
clrf ANSEL
clrf ANSELH

BANKSEL TRISA
clrf TRISA ; PORTA all output
clrf TRISB ; PORTB all output
clrf TRISC ; PORTC all output

BANKSEL SSPCON
bcf SSPCON, 5

;=== run timing loop ===
BSF PORTB,4
BCF PORTB,4
goto $-2
end


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