PCA84C122A PHILIPS [NXP Semiconductors], PCA84C122A Datasheet - Page 8

• Manufacturer Part Number: PCA84C122A
• Description: 8-bit microcontrollers for remote control transmitters
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
8
The Hardware Modulator is the main derivative part in the
PCA84C122. Figure 7 shows the internal architecture.
The Hardware Modulator generates a pulse train whereby
the ON-time of a pulse and the OFF-time between pulses
can be programmed in a number of clock cycles
(period = 1/f
1995 May 01
8-bit microcontrollers for
remote control transmitters
HARDWARE MODULATOR
control
f osc
osc
); see Figs 8 and 7.
internal bus (IB0 – 7)
OUT
ON-time
ON-time = 2 (on-time register = 0)
start
REGISTER
ON-TIME
(8)
pulse #1
OFF-time
Fig.8 Example pulse train output of OUT pin.
PULSE TIMER
(8)
pulse #2
Fig.7 Hardware Modulator.
REGISTER
OFF-TIME
CONTROL LOGIC
(8)
OFF-time = 4 (off-time register = 2)
end
interrupt
pulse #3
8
The number of pulses of the train is also programmable.
The time between pulse bursts is determined by software,
possibly using the standard 8-bit Timer/Counter.
8.1
There are three (derivative) registers and one (derivative)
counter that must be loaded from the core.
elapse time by software
PULSE COUNTER
PCA84C122; 222; 422; 622; 822
Interface between the 84CXXX core and
derivative logic
HIGH
(2)
REGISTER
CONTROL
(5)
PULSE COUNTER
number of pulses = 3
LOW
(8)
MCD254
MCD255 - 1
Product specification
OUT