Teledyne 100E Instruction Manual page 195

Model 100E Instruction Manual
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instrument's I C buss. The CPU controls the clock signal and determines when the
various devices on the bus are allowed to talk or required to listen. Data packets are
labeled with addresses that identify for which device the information is intended.
Keypad Decoder: Each key on the front panel communicates with a decoder IC via a
separate analog line. When a key is depressed the decoder chip notices the change of
state of the associated signal; latches and holds the state of all eight lines (in effect
creating an 8-bit data word); alerts the key-depress-detect circuit (a flip-flop IC);
translates the 8-bit word into serial data and; sends this to the I
Key-Depress-Detect Circuit: This circuit flips the state of one of the inputs to the I
interface chip causing it to send an interrupt signal to the CPU
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I C Interface Chip: This IC performs several functions:
• Using a dedicated digital status bit, it sends an interrupt signal alerting the CPU
that new data from the keyboard is ready to send.
• Upon acknowledgement by the CPU that it has received the new keyboard data,
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the I C interface chip resets the key-depress-detect flip-flop.
• In response to commands from the CPU, it turns the front panel status LEDs on
and off and activates the beeper.
• Informs the CPU when the optional maintenance and second language switches
have been opened or closed (see Chapter 5 for information on these options).
Display Data Decoder: This decoder the serial translates the data sent by the CPU (in
TTY format) into a bitmapped image which is sent over a parallel data bus to the display.
Display Controller: This circuit manages the interactions between the display data
decoder and the display itself. It generates a clock pulse that keeps the two devices
synchronized. It can also, in response to commands from the CPU turn off and/or reset
the display.
Additionally, for analyzers with the optional maintenance switch is installed (See Chapter
5), the display controller turns on an LED located on the back of the keyboard interface
PCA whenever the instrument is placed in maintenance mode.
Display Power Watchdog: The Model 100E's display can begin to show garbled
information or lock-up if the DC voltage supplied to it falls too low, even momentarily. To
alleviate this, a brown-out watchdog circuit monitors the level of the power supply and in
the event that the voltage level falls below a certain level, turns the display off, then on
resetting it
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I C Link To The Relay PCA: While the CPU's I
also routed through the keyboard/display interface, information passed to and from the
relay board via this channel is not recognized by, acted upon or affected by the circuitry
of the keyboard/display interface.
045150102 Rev XB1
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C communication with the relay board is
Theory Of Operation
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C interface chip.
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C
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