| Electronics > Beginners |
| N76E003 pin high/low takes larger time |
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| Vindhyachal.takniki:
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 |
| garethw:
Clock cycles and machine cycles are not the same. For example: Your clock is 16MHz. If your mcu is running 4 clock cycles per machine cycle then each instruction takes 1 / 4MHz = 250ns. The data sheet will explain how long each instruction will take in machine cycles as well as how long a machine cycle is. Sent from my iPhone using Tapatalk |
| garethw:
Checking the N76E003 datasheet reveals: 1 clock cycle per Machine cycle. SETB (set bit) = 4 Machine cycles CLR (clear bit) = 4 Machine cycles Hope that helps Gareth |
| Vindhyachal.takniki:
thanks |
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