PCA84C822AT Просмотр технического описания (PDF) - Philips Electronics
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PCA84C822AT Datasheet PDF : 24 Pages
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Philips Semiconductors
8-bit microcontrollers for
remote control transmitters
Product specification
PCA84C122; 222; 422; 622; 822
8 HARDWARE MODULATOR
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/fosc); see Figs 8 and 7.
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 Interface between the 84CXXX core and
derivative logic
There are three (derivative) registers and one (derivative)
counter that must be loaded from the core.
internal bus (IB0 – 7)
ON-TIME
REGISTER
(8)
OFF-TIME
REGISTER
(8)
CONTROL
REGISTER
(5)
f osc
control
PULSE TIMER
(8)
PULSE COUNTER
HIGH
(2)
PULSE COUNTER
LOW
(8)
CONTROL LOGIC
Fig.7 Hardware Modulator.
OUT
MCD255 - 1
OFF-time
OUT
start
ON-time
pulse #1
pulse #2
end
elapse time by software
interrupt
pulse #3
MCD254
ON-time = 2 (on-time register = 0)
OFF-time = 4 (off-time register = 2)
number of pulses = 3
1995 May 01
Fig.8 Example pulse train output of OUT pin.
8
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