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NEC PD754144 User Manual

Page 178

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CHAPTER 6 PERIPHERAL HARDWARE FUNCTION

178

User’s Manual U10676EJ3V0UM

(6) Notes on application of carrier generator (reload)

To output a carrier to the PTO2 pin, the time required for the initial carrier to be generated deviates by up to

one carrier clock after reloading (the contents of the no return zero buffer flag (NRZB) are transferred to the

no return zero flag (NRZ) by occurrence of the interrupt of timer counter channel 1, and the contents of NRZ

are updated to “1”).

This is because reloading is performed asynchronously to the carrier clock, as illustrated below in order to

hold constant the high-level period of the carrier.

1

0

0

1

Clock

NRZ

NRZB

Reloading by occurrence of interrupt

PTO2

0

TOUT F/F

1

0

1

0

1

0

1

0

0

1

Clock

NRZ

NRZB

Reloading by occurrence of interrupt

PTO2

0

TOUT F/F

1

0

1

0

1

Delay of up to one

carrier clock occurs.

0

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