National CP3BT26 - Manual (Page 206)

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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
27.1 VTU 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.
Figure 104. Versatile Timer Unit Block Diagram
INTCTL
0 15
MODE
0 15
Count1
TIO1
0 15
PERCAP1
Compare - Capture
DTYCAP1
Compare - Capture
C1 PRSC
Timer Subsystem 1
= =
7
Prescaler
Counter
I/O Control
INTPND
0 15
IO1CTL
0 15
IO2CTL
0 15
TIO2
I/O Control
Count2
TIO3
0 15
PERCAP2
Compare - Capture
DTYCAP2
Compare - Capture
C2 PRSC
= =
7
Prescaler
Counter
I/O Control
TIO4
I/O Control
Count4
TIO7
0 15
PERCAP4
Compare - Capture
DTYCAP4
Compare - Capture
C4RSC
= =
7
Prescaler
Counter
I/O Control
TIO8
I/O Control
Count3
TIO5
0 15
PERCAP3
Compare - Capture
DTYCAP3
Compare - Capture
C3 PRSC
= =
7
Prescaler
Counter
I/O Control
TIO6
I/O Control
Timer Subsystem 2 Timer Subsystem 3 Timer Subsystem 4
DS088