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38 lines
992 B
Markdown
38 lines
992 B
Markdown
# timer
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A simple timer with prescaler.
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## Introduction
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This core implements a simple timer with a prescaler. The prescaler
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allows measurement of time durations rather than cycles. If for
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example setting the prescaler to the clock frequency in Hertz, the
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timer will count seconds.
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## API
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The following addresses define the API for the timer:
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```
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ADDR_CTRL: 0x08
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CTRL_START_BIT: 0
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CTRL_STOP_BIT: 1
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ADDR_STATUS: 0x09
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STATUS_RUNNING_BIT: 0
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ADDR_PRESCALER: 0x0a
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ADDR_TIMER: 0x0b
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```
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## Details
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The core consists of the timer_core module (in timer_core.v) and a top
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level wrapper, timer (in timer.v). The top level wrapper implements
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the API, while the timer_core implements the actual timer
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functionality.
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The timer counter and the prescaler counter are both 32 bits.
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When enabled the counter counts down one integer value per cycle.
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The timer will stop when reaching final zero (given by prescaler times the initial value of the timer)
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and the running flag will be lowered.
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