Below is a response from Microchip Engineering Support Team for
your submitted ticket #: 1-20181. A description of the problem and
our proposed resolution is contained below.

Area: PICmicro Products
Product Group: PIC12F67X
Product: PIC12F675

Problem Description:
Hi, can you please explain further this reference in the 12F675
data sheet

Page 44, DS41190C

Register 7-2 ANSEL

bit 6-4 x11 FRC (clock derived from a dedicated internal oscillator = 500kHz
max)

What is the "dedicated internal oscillator" referred to, and why is the
distinction made between it and other sources of Fosc on Page 44 ?

thanks

Joe Colquitt
Auckland
New Zealand

Problem Resolution:

Dear Customer,

Please refer data sheet Page 41 (Section 7.1.4) for the AD Conversion
clock explanation.  The 10-BIT ADC in the PIC12F675 are request
minimum Tad with 1.6uS, and the conversion time need 12 Tad, so the
mininum conversion time are 1.6uS * 12Tad = 19.2uS.

You also will find the TABLE 7-1 show the Tad request for difference
operation frequency. At 5MHz frequency, you should set the ANSEL
<6:4> with Fosc/8 ( 5MHz/8= 1.6uS)  or at 4MHz frequence, the
minimum Tad are 4MHz/8 = 2uS.

When you set the ANSEL<6:4> with FRC mode (dedicated internal
oscillator = 500kHz max), the means the ADC will use own internal RC
oscillator for the ADC clock source, the minimum Tad will be 2uS
(500kHz) to 6uS

Microchip Engineering Support

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