Enhanced Comparator Datasheet CMPEn V 1.0
001-49131 Rev. *C
Enhanced Comparator
Copyright © 2009-2012 Cypress Semiconductor Corporation. All Rights Reserved.
PSoC® Blocks
Resources
CY8C21x45, CY8C22x45
Digital
0
API Memory (Bytes)
Analog CT
Analog SC
1
0
Flash
24
RAM
0
Pins (per
External I/O)
0...2
Features and Overview
Flexible input sources
Direct connection to digital PSoC block and interrupt
Output signal filtering
Output signal latching
The Enhanced Comparator (CMPEn) User Module provides a comparison of two input options. Both
inputs have the same set of possible connections to choose from, which enables you to select the polarity
of the output.
Figure 1.
CMPEn Block Diagram
Cypress Semiconductor Corporation
Document Number: 001-49131 Rev. *C
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Revised June 27, 2012
Enhanced Comparator
Functional Description
The ACE block provides a simple comparator which is at the heart of this user module. The comparator
has two inputs: a positive and a negative. Both the positive and negative inputs have identical connection
options at their input muxes. This enables you to create any combination of inputs with either negative or
positive polarity. You can compare the values of two pins by using a pin connected through the Analog
Column Input Mux, and another pin connected through the Analog Mux Bus. You can also compare an
input signal against a reference. A fixed 1.3V reference is provided internally by using the VBG analog
reference.
The analog compare output signal can pass through a noise filter. That is, a comparator output pulse with
width less than a selected number of clock cycles is filtered out. A “Noise Filter Bypass” property is also
available to disable this function.
An RS-Latch function is present in the analog comparator output data path. The latch block is shared
between two compare columns. The compare column 0 is the master input, and the compare column 1 is
the slave input. The master output (Q) and the slave output (QB) go back to compare column 0 and
compare column 1, respectively. If the master output is a primary output, then the 'high' signal from the
master channel clears the primary output (that is, the target is cut off for protection). The 'high' signal from
the slave channel sets the primary output (that is, the target is turned on for normal operation). The RSLatch function is bypassed if the RS-Latch is not selected. An RS_EN bit is used to enable the RS
function, and the RS_SEL bit in each column is used to select the RS function output.
DC and AC Electrical Characteristics
See the device datasheet for the electrical characteristics of this device.
Placement
The CMPEn block maps to any ACE02 or ACE03 block of the CY8C22x45 and CY8C21x45 device
families.
The analog column clock should be set to a source that delivers a maximum frequency of SysClk/2 for the
user module to function properly. You can clock the analog column with slow frequencies to limit the
oscillation produced when the two comparator inputs are near each other.
Parameters and Resources
There are seven parameters:
Pos Input
Neg Input
Noise Filter Bypass
Filter Clk Selection
Noise Filter Selection
Sync Latch Enable
Select Auto Trigger Source
Pos Input
The Positive Input can be selected from one of seven sources. These include the pin input multiplexer,
VBG (1.3V), Analog Mux Bus*, VDAC*, and the adjacent Analog CT block.
Note
* Only available on CY8C22x45 devices.
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Enhanced Comparator
Neg Input
The Negative Input can be selected from one of six sources. These include the pin input multiplexer,
VBG (1.3V), Analog Mux Bus*, VDAC*, and the adjacent Analog CT block.
Note
* Only available on CY8C22x45 devices.
Noise Filter Bypass
This parameter can enable or disable the comparator output Noise Filter.
Filter Clk Selection
This parameter gives you two options to clock the Noise Filter: System Clock or Column Clock.
Noise Filter Selection
This parameter determines the Noise Filter Width.
Sync Latch Enable
The Sync Latch Enable parameter enables latching the output signal. This parameter contains the
following selections:
Auto Trigger Global Enable
Description
Disable
Latching of output signal is disabled.
Enable
Latching of output signal is enabled. The Auto-Trig Selection System must be
activated. See Note ** at the end of the Parameters and Resources section.
Select Auto Trigger Source
The Select Auto-Trigger Source sets the current auto-trigger source for comparator output signal
latching. This parameter contains the following selections:
Select Auto Trigger Source
Description
TGL
The low 8-bit digital path is used as an auto-trigger source.
TGH
The high 8-bit digital path is used as an auto-trigger source.
TG16Bit
The combined high/low 8-bit digital path is used as an auto-trigger source.
TGINCMP
The GIE or internal comparators is used as an auto-trigger source.
PSoC digital blocks can be used as a trigger source for comparator output signal latching. The output
signal latches when a one-shot pulse occurs on the selected trigger source.
Note
** For example, the control registers of the Auto-Trig Selection System can be configured as:
TSCMPH = 1; // set CMP_H compare value
TSCR1 = 0x10; // select CMP_H source DBC01
TSCR0 = 0x02; // enable high channel trigger source
This means that the trig signal passes from the occupied DBC01 digital block. So that, for example,
the Counter8 User Module should be placed on DBC01 to generate an auto-trig signal.
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Enhanced Comparator
Application Programming Interfaces (APIs)
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.
Each time a user module is placed, it is assigned an instance name. By default, PSoC Designer assigns
CMPEn_1 to the first instance of this user module in a given project. It can be changed to any unique
value that follows the syntactic rules for identifiers. The assigned instance name becomes the prefix of
every global function name, variable, and constant symbol. In the following descriptions, the instance
name has been shortened to CMPEn for simplicity
Note
**In this, as in all user module APIs, the values of the A and X register may be altered by calling an API
function. It is the responsibility of the calling function to preserve the values of A and X before the call if
those values are required after the call. This “registers are volatile” policy was selected for efficiency
reasons. The C compiler automatically takes care of this requirement. Assembly language programmers
must ensure their code observes the policy, too. Though some user module API functions may leave A
and X unchanged, there is no guarantee they will do so in the future.
For Large Memory Model devices, it is also the caller's responsibility to preserve any value in the
CUR_PP, IDX_PP, MVR_PP, and MVW_PP registers. Even though some of these registers may not be
modified now, there is no guarantee that will remain the case in future releases.
CMPEn_Start
Description:
Performs all required initialization for this user module and turns on the comparator.
C Prototype:
void
CMPEn_Start(void)
Assembler:
lcall
CMPEn_Start
Parameters:
None
Return Value:
None
Side Effects:
See Note ** at the beginning of the API section.
CMPEn_Stop
Description:
Powers the user module off. The outputs are not driven.
C Prototype:
void
CMPEn_Stop(void)
Assembler:
lcall
CMPEn_Stop
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Enhanced Comparator
Parameters:
None
Return Value:
None
Side Effects:
See Note ** at the beginning of the API section.
CMPEn_EnableInt
Description:
Enables the interrupt associated with the Analog Comparator Bus.
C Prototype:
void
CMPEn_EnableInt(void)
Assembler:
lcall
CMPEn_EnableInt
Parameters:
None
Return Value:
None
Side Effects:
See Note ** at the beginning of the API section.
CMPEn_DisableInt
Description:
Disables the interrupt associated with the Analog Comparator Bus.
C Prototype:
void
CMPEn_DisableInt(void)
Assembler:
lcall
CMPEn_DisableInt
Parameters:
None
Return Value:
None
Side Effects:
See Note ** at the beginning of the API section.
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Enhanced Comparator
Sample Firmware Source Code
The sample code given here creates a simple comparator that generates an interrupt whenever the
Positive Input rises above the negative input:
;;----------------------------------------------------------------;; Sample Code for the CMPEn in Column 2
;;
;; The parameters are configured as such:
;; Interrupt: enabled
;; Power: switched on
;;----------------------------------------------------------------export _main
include "m8c.inc"
include "CMPEn.inc"
_main:
M8C_EnableGInt
call CMPEn_EnableInt
call CMPEn_Start
; Enable the interrupt
; and turn it on
The same code in C is:
//----------------------------------------------------------------// Sample Code for the CMPEn in Column 2
//
// The parameters are configured:
// Interrupt: enabled
// Power: switched on
//----------------------------------------------------------------#include <m8c.h>
#include "PSoCAPI.h"
void main(void)
{
M8C_EnableGInt;
CMPEn_EnableInt();
CMPEn_Start();
}
Document Number: 001-49131 Rev. *C
//Start the comparator
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Enhanced Comparator
Configuration Registers
The basic topology of the comparator sets most of the bits in the register configuration for the analog CT
block that is used.
Table 1.
Block CMPEn, Register: ACE_CR1
Bit
7
Value
0
6
1
5
4
3
Negative Input
2
1
0
Positive Input
The Positive and the Negative Inputs offer the same set of possible connections: the Analog Column
Input, the Analog Mux Bus, and the Analog SC block if an internal programmable reference is used.
Table 2.
Block CMPEn, Register: ACE_CR2
Bit
7
6
5
4
3
Value
2
1
1
0
Enable
The Enable bit turns on the comparator. This is controlled by the Start and Stop API functions.
Version History
Version
1.0
Note
Originator
DHA
Description
Initial version.
PSoC Designer 5.1 introduces a Version History in all user module datasheets. This section documents high level descriptions of the differences between the current and previous user module versions.
Document Number: 001-49131 Rev. *C
Revised June 27, 2012
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assumes all risk of such use and in doing so indemnifies Cypress against all charges.
Use may be limited by and subject to the applicable Cypress software license agreement.