Mode 0 (Interrupt on Terminal Count)

• This mode id selected if (D3 D2 D1) of CWR is (0 0 0).
• When this mode is selected OUT pin is initially low.
• The count value is loaded. GATE pin is made high, so counting is enabled.
• During counting, OUT pin remains low.
• On Terminal Count (TC) the OUT pin goes high, and remains high.
• During counting if GATE is made low, it disables counting. When GATE is made high, counting resumes.
• Effect of Gate: When gate is low, counting is disables and when gate is high, counting Enables (Resumes).

Mode 1 (Mono-stable Multi-vibrator)

• This mode id selected if (D3 D2 D1) of CWR is (0 0 1).
• When this mode is selected OUT pin is initially high.
• The count value is loaded. Counting begins ONLY when a rising edge is applied to the GATE. OUT pin goes low and remains low during counting.
• On Terminal Count (TC) the OUT pin goes high, and remains high.
• During counting if GATE is made low, it has no effect on the Counting.
• The GATE pin can be used as a Trigger. The Counter can be re-triggered by applying a rising edge on the GATE. This would Restart the counting, and hence re-trigger it.
• Effect of Gate: when gate is low, no effect; when gate is high (Trigger) it tarts Counting, can also re-trigger it.