Functional
Section 4
RCP-GPIO
page 4.1
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P/N 81905903860
F UNCTIONAL
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DE SCRIPTI ON
4.1 Introduction
The RCP-GPIO Control Panel contains one printed circuit board assem-
bly; the GPIO Interface Card. The GPIO Interface Card contains a micro-
processor that controls the panel's operation and communicates with the
routing switching system controller. The GPIO Interface Card also con-
tains the interface connections used by the external relays to the control
the routing switcher system. The following manual section contain a de-
tailed description of the GPIO Interface Card.
4.2 GPIO Interface Card
The GPIO Interface Card contains all of the circuitry necessary to commu-
nicate with the system controller and to interface with 32 inputs and 32
outputs. The circuitry on the GPIO Interface Card may be divided into the
following sections: Power Supply, Microprocessor, Clock, Reset, and
RS485 Communications. The GPIO Interface Card also contains circuitry
which scans the inputs and activates the corresponding output relays. The
following paragraphs explain each section in detail.
Power Supply
The power supply circuit on the GPIO Interface Card consists of a 7805
+5V regulator and filter capacitors. Unregulated DC voltage (7.5 to 9 VDC)
is supplied by an external power supply via J65. The voltage regulator
(U39) reduces the voltage to 5.0 VDC. C10 and C9 provide filtering for the
input and output of the regulator. Bypass capacitors (0.1 uF) are scattered
about the assembly to provide power supply bypassing for the individual
integrated circuits (ICs). Unregulated voltage (Vext) is also provided to the
output relay circuits.
Microprocessor
The heart of the GPIO Interface Card is the Motorola 68HC11 micropro-
cessor (U35). This IC contains the microprocessor and peripheral circuitry
used to operate the control panel. In addition, the 68HC11 contains a
PROM loaded with the software used to operate the control panel. The
68HC11 is operated in the multiplexed mode. In this mode port B (U35 pin
35-42) provides the address byte (A0-A2). Port C (U35 pins 9-16) provides
the data byte (D0-D7).
