Sine Systems RFC-1/B Instruction Book

Section 6 — Circuit Description
RFC-1
The heart of the RFC-1 is a Motorola MC68HC711E9 microcontroller. This is a complete
computer containing a CPU, program ROM, RAM, a timer, a fault monitor, parallel I/O and
an A-D converter. The CD22202 (or 75T202) (U2) DTMF decoder and the UDN2981A (U6) relay
buss driver connect directly to it and communicate in "parallel." The ISD2590P (U4) speech
synthesizer is connected to a parallel port on the microcontroller and to a serial-to-parallel
shift register (U10) which is used to assist in the transfer of data.
U8 and U9 are standard voltage regulators and provide the three DC voltages needed by the
RFC-1. D6 is used to shift the ground reference point of the power supply. D5 and D7 are
used only to absorb transient voltage spikes on the +10 and +6.9 volt busses, respectively.
The relay buss protocol in the RFC-1 is simple. J3 pins 6 through 11 form a six bit parallel
binary, positive true, word which identifies the currently selected channel. Pin 6 is the least
significant bit. Pin 12 is normally low but goes high when an "ON" command is activated.
Pin 13 is normally low but goes high when an "OFF" command is activated. Pins 12 and 13
drive the control relays directly. The voltage level on this buss is somewhat higher than the
standard +5 volt logic level to allow for the voltage drop of the telemetry relay driver and
isolation diodes on the RP-8 relay panels.
In the idle condition (on hook) the RFC- 1 selects channel “ 63" which makes J3 pins 6 through
11 all high. The "Local Control" pushbutton on the RP-8 relay panels is normally open and is
bridged across J3 pin 11 and ground. The microprocessor checks the logic level on pin 11 and
if it goes low it assumes that a "Local Control" pushbutton has been pressed and it configures
the RFC-1 for the local control mode. This connects the local telephone to the unit through a
source of DC so the telephone's keypad will work.
U-3 is a "low voltage interrupt" (LVI) device which resets the microprocessor if the power
supply voltage falls below a specific value.
RP-8
Each RP-8 panel contains two "three bit binary to one-of-eight" decoders. One (Ul) is
connected to the most significant three bits of the channel selection buss and the other (U2) is
connected to the least significant three bits of the buss. Ul and U2 are similar in operation
but U 1 has "active low" outputs and U2 has "active high" outputs. The output of U 1 feeds the
"Block Selection" Jumper. The upper three bits contain the information that determines in
which block of channels the selected channel falls. If this matches the jumper for the
particular panel, a "low" logic level is applied to U2 pin 11 enabling it to decode the first three
bits of the address and route the decoded result (active high) to the relay driver, U3. U3 has 8
inputs and 8 open-collector outputs. A high logic level from the selected output of U2 causes
the corresponding open-collector output of U3 to "pull down." This turns on one of the eight
reed relays and allows the telemetry to be read for that channel. It also pulls down the low
side of the control relays for that channel. The high side of the control relays are connected
to the "ON" and "OFF" lines coming from the RFC- 1 which can then cause the selected control
relays to operate.
3.00.0
Circuit Description
page 6.1

Sine Systems RFC-1/B Specifications

General

Brand	Sine Systems
Model	RFC-1/B
Category	Remote Control
Language	English