Fluke Biomedical 960CD-220 - Manual (Page 16)

Victoreen 960CD-220,221,222,223
Operators Manual
2-2
Device selection is accomplished by two IC's, Z36 and Z37. They decode the sixteen-device selects line
that select external devices on the 960MB or 961MB Motherboard bus.
2.3 Communication Support
Refer to Drawing 960CD-220-13, Sheet 3 in Appendix B. The controller contains up to three
asynchronous serial communications, MC6850 ACIA ports. ACIA Z6, port 1, is normally configured to
communicate via a Victoreen communications loop. For test purposes, port 1 can be configured to
operate as an RS-232C channel. ACIA Z5, port 2, is also configured to communicate via a Victoreen
communications loop. It can be configured to operate as a transmit only fiber optic channel. ACIA Z4, port
3, can be configured to operate as an RS-232C channel.
• Controller Module 960CD-221 utilizes the RS-232C channel.
• Controller Module 960CD-222 utilizes port 3 as a receive only fiber optic channel.
• Controller Module 960CD-223 is the only module which utilizes the transmit only fiber optic channel.
Z22 and Z23 form a time out circuit that ensures that the communication loops are not held in an active
state due to a malfunction of the ACIA or its associated circuitry.
PNP transistor Q11 drives the transmit LED in optical coupler Z32. The photosensitive transistor in Z32
receives the optical signal from the LED, and drives the communication loop. This electrically isolates the
communication loop from the rest of the controller's electronics. Power for the loop is provided by an
external floating 30 VDC potential and is applied between +VL and -VL. In the quiescent state, +TX is
pulled to -VL by a resistor tied to -VL. -TX is pulled to +VL by a resistor tied to +VL. When the loop is
driven, +TX is pulled to +VL by Q2, -TX is pulled to -VL by Q4. Q2 is driven by Q8 and Q4 is driven by
Q6. Transistor Q6 is driven by the output of opto-coupler Z32.
The receive portion of the communication loop is connected via a cable to a transmitter as described
above, but it is placed in a location which is remote from the 960CD controller module. The quiescent
state of +TX is a negative potential. The quiescent state of -TX is a positive potential. For communication
between units, the transmit and receive lines are connected so that +TX of one is connected to the +RX
of the other and -TX of one is connected to -RX of the other. Therefore, the quiescent state of the receive
circuitry LED RX2 is reverse biased, LED on. The phototransistor of Z13 turns on, pulling the receive data
input of the ACIA to a logic 0 level. The +TX2, -TX2, +RX2 and -RX2 of the second Victoreen
communication loop circuits, if installed, operate in the same manner.
Controller Module 960CD-223 contains fiber optic transmitter J5B. The transmitter is driven by transistor
Q10 instead of a Victoreen loop driver like the one used for port 2. This is a transmit only port that is
utilized for nuclear safety-related applications. The fiber optics transmitter is a molded connector
assembly housing a transmitting LED that terminates directly in a fiber optic cable assembly.
Controller Module 960CD-222 contains fiber optic receiver J5A. The receiver contains a phototransistor in
a molded connector. The connector also contains a comparator that buffers the phototransistor output. In
order for the fiber optics receiver to function, jumper W6 must be in the B to C position. Jumper W6
selects either the fiber optics receiver or the RS-232C receiver mode.
Controller Module 960CD-221 contains the RS-232C receiver Z2. Z2 and Z3 enable port 1 and/or port 3's
RS-232C port function depending on the position of jumper W6. Jumper W6 must be in the A to B position
to select the RS-232C port function.
2.4 Display/Channel ID
Refer to Drawing 960CD-220-13, sheet 4, in Appendix B. A counting circuit, consisting of Z1, Z33, and
Z34, provides 100 HZ, 4 HZ, and switchable baud rates. The circuit is used to select a BIT RATE (baud