PIC16C923T-08I/SP View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

PIC16C923T-08I/SP

8-Bit CMOS Microcontroller with LCD Driver

Microchip Technology 

12.8 Use of the CCP Trigger

An A/D conversion can be started by the “special event

trigger” of the CCP1 module. This requires that the

CCP1M3:CCP1M0 bits (CCP1CON<3:0>) be pro-

grammed as 1011 and that the A/D module is enabled

(ADON bit is set). When the trigger occurs, the

GO/DONE bit will be set, starting the A/D conversion,

and the Timer1 counter will be reset to zero. Timer1 is

reset to automatically repeat the A/D acquisition period

with minimal software overhead (moving the ADRES to

the desired location). The appropriate analog input

channel must be selected and the minimum acquisition

done before the “special event trigger” sets the

GO/DONE bit (starts a conversion).

If the A/D module is not enabled (ADON is cleared),

then the “special event trigger” will be ignored by the

A/D module, but will still reset the Timer1 counter.

12.9 Connection Considerations

If the input voltage exceeds the rail values (VSS or VDD)

by greater than 0.2V, then the accuracy of the conver-

sion is out of specification.

An external RC filter is sometimes added for anti-alias-

ing of the input signal. The R component should be

selected to ensure that the total source impedance is

kept under the 10 kΩ recommended specification. Any

external components connected (via hi-impedance) to

an analog input pin (capacitor, zener diode, etc.) should

have very little leakage current at the pin.

PIC16C9XX

12.10 Transfer Function

The ideal transfer function of the A/D converter is as fol-

lows: the first transition occurs when the analog input

voltage (VAIN) is Analog VREF / 256 (Figure 12-5).

FIGURE 12-5: A/D TRANSFER FUNCTION

FFh

FEh

04h

03h

02h

01h

00h

Analog input voltage

© 1997 Microchip Technology Inc.

DS30444E - page 87

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