User manual

Chapter 3 Software Overview

You can configure a counter to count either falling or rising edges of the

selected internal timebase, SOURCE input, GATE input, or next lower

order counter signal.

You can use the counter GATE input to gate counting operations. After you

software-configure a counter for an operation, a signal at the GATE input

can start and stop the counter operation. There are nine gating modes

available in the Am9513:

• No Gating—Counter is started and stopped by software.

• High-Level Gating—Counter is active when its gate input is at

high-logic state. The counter is suspended when its gate input is

at low-logic state.

• Low-Level Gating—Counter is active when its gate input is at

low-logic state. The counter is suspended when its gate input is

at high-logic state.

• Rising Edge Gating—Counter starts counting when it receives a

low-to-high edge at its gate input.

• Falling Edge Gating—Counter starts counting when it receives a

high-to-low edge at its gate input.

• High Terminal Count Gating—Counter is active when the next lower

order counter reaches terminal count (TC) and generates a TC pulse.

• High-Level Gate N+1 Gating—Counter is active when the gate input

of the next higher-order counter is at high-logic state. Otherwise, the

counter is suspended.

• High-Level Gate N–1 Gating—Counter is active when the gate input

of the next lower order counter is at high-logic state. Otherwise, the

counter is suspended.

• Special Gating—The gate input selects the reload source but does not

start counting. The counter uses the value stored in its internal Hold

internal Load register when the gate input is low.