N76E003 pin high/low takes larger time

Thread Starter

Vindhyachal Takniki

Joined Nov 3, 2014
1. I am using N76E003, keil v9.51 . Controller is running at 16Mhz, I can measure this on Clockout pin by DSO.

2. Internal clock diagram shows, Clockout frequency & peripheral frequency is same.

3. Timers works correctly accroding to 16Mhz clock.

4. Issue I faced is when I write:

P04 = 0; or P04 = 1;

it takes around 250ns as measured on DSo with 10x probe for single instruction.

5. Disassembly on keil shows:

C:0x07FE C284 CLR P04(0x80.4)
C:0x0800 D284 SETB P04(0x80.4)

6. These are single cycle instruction. What I dont understand is when cpu is running at 16Mhz, single cycle time should be 1/16Mhz i.e 62.5ns, but on DSO it takes 250ns around

7. Then why pin high low takes large time


Joined Mar 10, 2018
Sounds like internal clock divider set to 4.

For test you do a set followed by a clear, triggering scope on + edge,
and measure the high time to be 250 nS ?

Regards, Dana.