45181 Parallax Inc, 45181 Datasheet - Page 97

• Manufacturer Part Number: 45181
• Description: SX TECH TOOL KIT NO POWER
• Manufacturer: Parallax Inc
• Series: SXr
• Type: Microcontrollerr

Specifications of 45181

• Contents: SX Book, SX Key, SX Tech Board, Samples, Resonators, Cable and Manual
• Product: Microcontroller Basic Stamps
• Operating Supply Voltage: 5 V
• For Use With/related Products: SX MCUs
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The block diagram in Figure 16 – SX48/52 Multi-Function Timers, below, shows the components of one
timer:
Registers R1, R2 and the capture registers can be accessed by mov !rb, w (Timer1), or mov !rc, w
(Timer2) instructions. The remaining registers cannot be accessed via software.
Timer 1 shares its input and output lines with the Port B pins 4...7, and Timer 2 shares its input and
output lines with the Port C pins 0...3. If a timer is active, those pins can no longer used for "regular"
I/O purposes.
10.3.1 PWM Mode
In this mode, the timer generates a square wave signal with programmable frequency, and duty cycle.
For this purpose, the contents of the two comparison registers determine for how long the signal is high,
and low.
The 16-bit counter starts with a value of 0, and keeps incrementing until it has reached the value of R1.
Then, the counter is reset to 0, the output is toggled, and (if enabled) an interrupt is generated.
Next, the counter keeps incrementing until it reaches the value of R2. Again, the counter is reset to 0, the
output signal is toggled, and an interrupt is triggered (if enabled).
These two steps are repeated continuously. The contents of R1 and R2 determine the frequency and the
duty cycle of the generated output signal. When R1 and R2 contain the same value, a square wave with
a duty cycle of 50% is generated. In order to generate a signal with a constant frequency, and a varying
System Clock
External Clock
(RB7/RC3)
Capture 1 (RB4/RC0)
Capture 2 (RB5/RC1)
8-Bit Prescaler
Multiplexer
Figure 16 - SX48/52 Multi-Function Timers
or Capture Register (2)
16-Bit Comparison R2
10 SX Special Features and Coding Tips
16-Bit Capture Register (1)
16-Bit Comparator
SX-Key/Blitz Development System Manual 2.0 Parallax, Inc. Page 97
16-Bit Counter
16-Bit Comparison Register
R1
Output (RB6/RC2)
Compare
Interrupt
Capture
Interrup
t