Ramsey Electronics URC1 Owner's Manual page 5

HOW THE URC1 WORKS:
Take a look at the URC1's schematic diagram as we walk through the circuit.
As you can see there is not much to the universal remote control, most of the
work is internal to the IC's.
The real heart of the circuit is U6 the microcontroller IC. This 20 pin IC can
perform an amazing amount of tasks, quickly as well as reliably. This IC
controls all of the outputs as well as the display, and also processes the
codes decoded from U5, the tone decoder IC.
U5, the tone decoder IC does most of the complicated work in this kit.
Internally this chip has a set of counters that latch different outputs depending
on the tones. The internal counters are referenced to a television colorburst
crystal operating at 3.579 Mhz. This reference frequency is used also as the
clock frequency to pin 10 of U5 the microprocessor.
U1, and U3 are serial shift registers. Data is clocked into them bit by bit from
the microprocessor, and then latched to the outputs by a change in state on
the LDS line. One of the outputs from these chips is used to deliver a tone
output for confirmation of commands.
U4 is a digitally controlled dual potentiometer. A very versatile device, it can
control volumes, levels, tuning on most Ramsey kits, thermostats, and
whatever else a pot can be used in.
U7 is a quad serial digital to analog converter. This provides the 0-5VDC
levels in 256 steps. These levels can be used to control dimmers,
thermostats, motor speed controllers, and anything else you can come up
with.
U2 is the display driver IC, this is also loaded serially with information to what
the displays show. It controls six digits of the display as well as the error code
LEDs.
VR1 and the surrounding parts form a simple voltage regulator to supply a
steady 5 VDC to the ICs in this circuit. By using this scheme, we can have a
wide range of supply voltages, from 7 volts to 15 volts DC.
URC1 • 5