National CP3BT26 manual Versatile Timer Unit VTU, VTU Functional Description, 206

CP3BT26

27.0 Versatile Timer Unit (VTU)

The Versatile Timer Unit (VTU) contains four fully indepen- dent 16-bit timer subsystems. Each timer subsystem can operate either as dual 8-bit PWM timers, as a single 16-bit PWM timer, or as a 16-bit counter with 2 input capture chan- nels. These timer subsystems offers an 8-bit clock prescaler to accommodate a wide range of system frequencies.

The VTU offers the following features:

„The VTU can be configured to provide:

—Eight fully independent 8-bit PWM channels

—Four fully independent 16-bit PWM channels

—Eight 16-bit input capture channels

„The VTU consists of four timer subsystems, each of which contains:

—A 16-bit counter

—Two 16-bit capture / compare registers

—An 8-bit fully programmable clock prescaler

„Each of the four timer subsystems can operate in the fol- lowing modes:

—Low power mode, i.e. all clocks are stopped

—Dual 8-bit PWM mode

—16-bit PWM mode

—Dual 16-bit input capture mode

„The VTU controls a total of eight I/O pins, each of which can function as either:

—PWM output with programmable output polarity

—Capture input with programmable event detection and timer reset

„A flexible interrupt scheme with

—Four separate system level interrupt requests

—A total of 16 interrupt sources each with a separate in- terrupt pending bit and interrupt enable bit

27.1VTU FUNCTIONAL DESCRIPTION

The VTU is comprised of four timer subsystems. Each timer subsystem contains an 8-bit clock prescaler, a 16-bit up- counter, and two 16-bit registers. Each timer subsystem controls two I/O pins which either function as PWM outputs or capture inputs depending on the mode of operation. There are four system-level interrupt requests, one for each timer subsystem. Each system-level interrupt request is controlled by four interrupt pending bits with associated en- able/disable bits. All four timer subsystems are fully inde- pendent, and each may operate as a dual 8-bit PWM timer, a 16-bit PWM timer, or as a dual 16-bit capture timer. Figure 104 shows the main elements of the VTU.

15	0	15		0	15	0
	MODE		INTCTL			IO1CTL
		15		0	15	0
			INTPND			IO2CTL

Timer Subsystem 1

7

C1 PRSC

= =

Prescaler

Counter

15 0

Count1

Compare - Capture

PERCAP1

Compare - Capture

DTYCAP1

Timer Subsystem 2

7

C2 PRSC

= =

Prescaler

Counter

15 0

Count2

Compare - Capture

PERCAP2

Compare - Capture

DTYCAP2

Timer Subsystem 3

7

C3 PRSC

= =

Prescaler

Counter

15 0

Count3

Compare - Capture

PERCAP3

Compare - Capture

DTYCAP3

Timer Subsystem 4

7

C4RSC

= =

Prescaler

Counter

15 0

Count4

Compare - Capture

PERCAP4

Compare - Capture

DTYCAP4

I/O Control	I/O Control	I/O Control	I/O Control	I/O Control	I/O Control	I/O Control	I/O Control
TIO1	TIO2	TIO3	TIO4	TIO5	TIO6	TIO7	TIO8

DS088

Figure 104. Versatile Timer Unit Block Diagram

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