PIC18F23K22-ESLASHML datasheet(317/496 Pages) MICROCHIP

317 / 496 page

 2010 Microchip Technology Inc.

Preliminary

DS41412C-page 317

PIC18(L)F2X/4XK22

19.0 CHARGE TIME

MEASUREMENT UNIT (CTMU)

The Charge Time Measurement Unit (CTMU) is a

flexible analog module that provides accurate

differential time measurement between pulse sources,

as well as asynchronous pulse generation. By working

with other on-chip analog modules, the CTMU can be

used to precisely measure time, measure capacitance,

measure relative changes in capacitance or generate

output pulses with a specific time delay. The CTMU is

ideal for interfacing with capacitive-based sensors.

The module includes the following key features:

• Up to 28(1) channels available for capacitive or

time measurement input

• On-chip precision current source

• Four-edge input trigger sources

• Polarity control for each edge source

• Control of edge sequence

• Control of response to edges

• Time measurement resolution of 1 nanosecond

• High precision time measurement

• Time delay of external or internal signal

asynchronous to system clock

• Accurate current source suitable for capacitive

measurement

The CTMU works in conjunction with the A/D Converter

to provide up to 28(1) channels for time or charge

measurement, depending on the specific device and

the number of A/D channels available. When config-

ured for time delay, the CTMU is connected to the

C12IN1- input of Comparator 2. The level-sensitive

input edge sources can be selected from four sources:

two external input pins (CTED1/CTED2) or the ECCP1/

(E)CCP2 Special Event Triggers.

Figure 19-1 provides a block diagram of the CTMU.

FIGURE 19-1:

CTMU BLOCK DIAGRAM

Note 1: PIC18(L)F2XK22 devices have up to 17

channels available.

CTED1

CTED2

Current Source

Edge

Control

Logic

CTMUCONH/CTMUCONL

Pulse

Generator

A/D Converter

Comparator 2

Input

ECCP2

ECCP1

Current

Control

ITRIM<5:0>

IRNG<1:0>

CTMUICON

CTMU

Control

Logic

EDGEN

EDGSEQEN

EDG1SELx

EDG1POL

EDG2SELx

EDG2POL

EDG1STAT

EDG2STAT

TGEN

IDISSEN

CTPLS

Comparator 2 Output

CTTRIG

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