# 555 Timer @1MHz

i am very new to electrical engineering and super unsure what to buy, because this is my first practical project...

I want to implement a hardware timer with ~1MHz frequency for the HCTL-2022 chip. For this i would use the TCL555CP Timer, two resistors with 500 Ohm and 1 kOhm, a capacitor of 1nF and a smoothing capacitor of 10nF as shown in this wikipedia article.

The usage:
The HCTL-2022 is reading a optical incremental encoder with ~4kppm. I want to read the HCTL with the Arduino Mega 2560. I need the timer because i think the microcontroller is not able to create a frequency that high.

Is this setup ok for my task? Is there a better / easier way? Can you give me any tips? Do i have to pay attention which capacitor or resistor i am buying?

Thanks for your time and help!

• "i think the microcontroller is not able to create a frequency that high." Why? Are you running it off a watch crystal? – Ignacio Vazquez-Abrams Oct 16 '15 at 8:44
• i am reading data from the HCTL and transfering them over Serial to a desktop application. because of that i thought it is no possible to hold a frequency of 1 MHz while doing timing relevant operations. – Jens Oct 16 '15 at 8:48
• But that's what the timer peripherals are for. – Ignacio Vazquez-Abrams Oct 16 '15 at 8:49
• While you can get 1 MHz from the TCL555P, please read p.9, "Operating Characteristics", fmax for the component values. – WhatRoughBeast Oct 16 '15 at 16:18