PIC10LF322T-EMCSQTP datasheet(131/210 Pages) MICROCHIP

131 / 210 page

 2011 Microchip Technology Inc.

Preliminary

DS41585A-page 131

PIC10(L)F320/322

20.1

NCOx OPERATION

The NCOx operates by repeatedly adding a fixed value

to an accumulator. Additions occur at the input clock

rate. The accumulator will overflow with a carry

periodically, which is the raw NCOx output. This

effectively reduces the input clock by the ratio of the

addition value to the maximum accumulator value. See

Equation 20-1.

The NCOx output can be further modified by stretching

the pulse or toggling a flip-flop. The modified NCOx

output is then distributed internally to other peripherals

and optionally output to a pin. The accumulator overflow

also generates an interrupt.

The NCOx output creates an instantaneous frequency,

which may cause uncertainty. This output depends on

the ability of the receiving circuit (i.e., CWG or external

resonant

converter

circuitry)

average

the

instantaneous frequency to reduce uncertainty.

20.1.1

NCOx CLOCK SOURCES

Clock sources available to the NCOx include:

•HFINTOSC

•FOSC

•LC1OUT

• NCO1CLK pin

The NCOx clock source is selected by configuring the

NxCKS<1:0> bits in the NCOxCLK register.

20.1.2

ACCUMULATOR

The Accumulator is a 20-bit register. Read and write

access to the Accumulator is available through three

registers:

• NCOxACCL

• NCOxACCH

• NCOxACCU

20.1.3

ADDER

The NCOx Adder is a full adder, which operates

asynchronously to the clock source selected. The

addition of the previous result and the increment value

replaces the accumulator value on the rising edge of

each input clock.

20.1.4

INCREMENT REGISTERS

The Increment value is stored in two 8-bit registers

making up a 16-bit increment. In order of LSB to MSB

they are:

• NCOxINCL

• NCOxINCH

Both of the registers are readable and writeable. The

Increment registers are double-buffered to allow for

value changes to be made without first disabling the

NCOx module.

The buffer loads are immediate when the module is dis-

abled. Writing to the MS register first is necessary

because then the buffer is loaded synchronously with

the NCOx operation after the write is executed on the

lower increment register.

EQUATION 20-1:

Note:

The increment buffer registers are not user-

accessible.

FOVERFLOW

NCO Clock Frequency

Increment Value



----------------------------------------------------------------------------------------------------------------

n = Accumulator width in bits

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