In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Zoot wrote:

Sorry not to get back on this thread sooner...

Where are you getting 3 cycles? A pin-edge interrupt will take 5 cycles, possibly 6

[quote=""] The SX chip will activate the interrupt routine exactly 5 clock cycles in Turbo mode or exactly 10 
clock cycles in compatible mode after a Wake-Up Edge Detection event occurs. This deterministic 
feature allows for nearly jitter-free interrupt response. Latency may vary by as much as +1 
instruction cycle when interrupting on external asynchronous events, thus a high clock speed may 
be necessary to lessen the effects.[/quote]

Second, these instructions in SX/B are actually many more assembly instructions than you think:

[code]
Int_Check = WKPND_B
    If Int_Check <>%00000001 Then ISR_Exit 'Check to make sure that interrupt due to pin RB.0

    SX_CLK = 1

    SX_CLK = 0
[/code]

Look at the list file (view list) and you'll see. If NOCODE isn't used, then you'll see even more.

Now, if you are ONLY checking for ONE possible pin on interrupt, and you've turned RTCC interrupts off, then you don't need to actually check WKPND_B, only clear it (the interrupt won't happen except on that one pin change):

[code]
W = WKPND_B ' 4 cycles
SX_CLK = 1    ' 1 cycle
NOP              ' 1 cycle
SX_CLK = 0  ' 1 cycle
[/code]

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