NEC PD754144 User Manual
Page 178
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