Fluke Biomedical 960CI-200 - Manual (Page 11)

Theory of Operation
4
4-1
Section 4
Theory of Operation
4.1 Theory of Operation
Figure 1-1 is the block diagram for the 960CI-200 Communications Isolator. The circuitry is explained in the following
paragraphs. Refer to the schematic diagrams in Appendix B to understand the circuit explanations.
4.2 Address Allocation
Table 4-1 lists the address allocations for the internal circuitry of the isolator.
Table 4-1. Address Allocations
Address Allocation
300 Loop 1 (to computer)
400 Loop 2 (to computer)
500 Loop 3 (from computer)
200 Channel ID
2000 – 7FFF RAM
8000 – FFFF PROM
4.3 Isolator
Refer to schematic 960CI-200-13
REG1 is the +5 VDC power supply that provides power. The customer supplies the 120 VAC input power. SW4 is the
120 VAC power switch. Surge and spike protection is provided by D1.
Optical receiver F01 and IC U21 provides a TTL level signal to the RX input of U17. IC U17 is used strictly for receiving
(RX). The transmit (TX) line is not active or connected. The signal input for U21 is the optically isolated serial data
from the safety related monitor (SRD). Signal decoding for the communications isolator comes from U6. The
decoded instructions are used to generate the enable signals for the three communication ports.
4.4 Channel ID
SW3 is an array of 6 switches that are used to set the channel identification code. It can be set from 00 HEX to 3F HEX
(64 settings). U15 is an octal buffer chip with a 3 state output. It is enabled for reading the CHANNEL ID.
When U7 receives a READ instruction, data will be transferred to the microprocessor.