* Question
What are the characteristics of the S3C2440A timer?
* Answer
The S3C2440A is a 32-bit ARM920T-based microcontroller developed by Samsung (now part of the Samsung Exynos family), widely used in embedded systems. Its timer module is a key peripheral, offering multiple independent timer channels for various timing, counting, and PWM (Pulse Width Modulation) applications.
Below is a detailed breakdown of the characteristics of the S3C2440A timer:
1. Timer Overview
The S3C2440A includes 5 independent 16-bit timer/counter units:
Timer 0–3: Can generate interrupts, measure intervals, and produce PWM signals.
Timer 4: Typically used as an internal tick counter, not connected to external output.
2. Clock Source and Prescaling
Timers use PCLK (peripheral clock) as the base clock.
Two levels of frequency division:
Prescaler (1st stage): Shared among timers 0–3; divides PCLK.
MUX divider (2nd stage): Per-timer divider (1, 2, 4, 8, 16).
This allows for flexible clock generation suited for slow or high-speed timing.
3. Operating Modes
Interval Timer Mode: Generates periodic interrupts for software timing.
PWM Mode: Generates pulse-width modulated output for motor control, audio, etc.
One-Shot Mode: Fires once after a defined time period.
Timer/Counter Mode: Can count external events (in capture mode, limited).
4. Register Configuration
Each timer has a set of control and data registers:
Register | Function |
TCFG0/1 | Timer configuration (prescaler, divider) |
TCON | Timer control (start/stop, manual update) |
TCNTBn | Timer count buffer (initial value) |
TCMPBn | Compare buffer (for PWM duty cycle) |
TCNTOBn | Current timer count value |
n denotes the timer number (0–4).
5. PWM Capabilities
Timers 0–3 can output PWM signals via the TCMPBn register.
Output toggles when TCNTOBn reaches TCMPBn.
Timer output pins (TOUT0–TOUT3) provide physical PWM output.
6. Interrupt Support
Each timer (0–4) can trigger an individual interrupt upon timer underflow (when counter reaches 0).
Useful for time-based software scheduling, real-time clock, event polling.
7. Timer 4 Specific Note
Timer 4 is designed for internal use only.
Does not output PWM or connect to external pins.
Typically used for OS tick generation or system delays.
Summary Table
Feature | Description |
Number of Timers | 5 (Timer 0–4) |
Bit Width | 16-bit counters |
Clock Source | PCLK (divided by prescaler and mux) |
Modes | Interval, One-shot, PWM |
PWM Output | Supported on Timer 0–3 via TOUT0–3 |
Interrupts | One per timer |
Timer 4 | Internal use only, no external output |
Application Examples
Generating software ticks (Timer 4 with OS kernel)
Driving PWM-based devices (LEDs, motors)
Measuring time intervals or delays
Creating time-triggered events via interrupts
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