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One-Shot
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OneShot v1.2
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General Purpose One-Shot
© 2004-2005 Ilya Mamontov.
| Resources |
PSoC™ Blocks |
API Memory (Bytes) |
Pins (per External I/O and Clock) |
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|---|---|---|---|---|---|---|
| Digital |
Analog CT |
Analog SC |
Flash |
RAM |
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| CY8C29/27/24/22xxx |
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| 8-bit |
1 |
8 |
0 |
2 |
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| CY8C26/25xxx |
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| 8-bit |
1 |
8 |
0 |
2 |
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•
Data input clocking up to 48 MHz
•Data Input can be inverted
•3 variations: One-shot Classic, Pulse Width Discriminator and Pulse Width Discriminator with Inverted Output
A one-shot (also known as a "univibrator" or "monostable multivibrator") is a device that produce a single pulse in response to an input signal. It can be used for reshaping of input pulses and generation of single pulses with a required duration.
A Pulse Width Discriminator produces an output pulse in response to an input pulse of a certain duration. Input pulses less than the specified duration are ignored.
Both the One-shot and Pulse Width Discriminator can be used for de-bouncing. Usually the source of bounce is a comparator that creates multiple triggers when the input levels are crossing. If this signal is routed to a Counter User Module, false triggers will be counted. Typical usage of a One Shot User Module is between a Comparator's output and a Counter's input.
Note. Incoming pulses are sampled by the rising edge of the clock. If the input pulse is not coincident with a clock rising edge then it will be ignored.
Operation of the One-shot Classic is shown in Figure 2. The incoming data to the Input is sampled by the rising edge of the Clock. The first incoming "0" triggers the output low for 8 cycles; then each following "0" prolongs the low state for 8 cycles. All reactions are delayed by one cycle.
Operation of the Pulse Width Discriminator is shown in Figure 3 and 4. The incoming data to the Input is sampled by a rising edge of Clock. Only eight or more of adjacent "0" set the output to low, the first incoming "1" triggers the output to high. All reactions are delayed by one cycle.
Operating of One-shot Classic and Pulse Width Discriminator as a de-bouncing unit is shown in Figure 5 and 6
The One-shot consumes one Digital PSoC block per 8 bits of resolution. Each block is given a symbolic name by the Device Editor during placement. The API qualifies all register names with the user assigned name.
An additional consideration, in selecting a placement location, is that the OneShot User Module should not be placed in a low adjacent position near any CRCPRS-based module (PRS, CRC16 or another OneShot).
Once a One-shot User Module has been selected and placed using the Device Editor, the following parameters may be set:
The Clock parameter is selected from 1 of 15 sources. These sources include the 48 MHz oscillator (5.0V operation only), lower frequencies (24V1 and 24V2) divided down from the 24 MHz system clock, other PSoC blocks, and external inputs routed through global inputs and outputs.
This parameter sets the ClockSync type "SysClk Direct", "Sync to SysClk", "Sync to SysClk*2" or "Unsynchronized".
This parameter sets the operating type "One-shot Classic", "Pulse Width Discriminator" or "Pulse Width Discriminator (Inverted)" as described in the functional description above.
This parameter gives the user the option to invert the Input.
The Application Programming Interface (API) routines are provided as part of the user module to allow the designer to deal with the module at a higher level. This section specifies the interface to each function together with related constants provided by the "include" files.
Description:
C Prototype:
void OneShot8_Start(void)
Assembler:
call OneShot8_Start
Parameters:
Return Value:
Side Effects:
Description:
C Prototype:
void OneShot8_Stop(void)
Assembler:
call OneShot8_Stop
Parameters:
Return Value:
Side Effects:
