Teledyne GFC 7001E Keyboard/Display Interface Electronics, Keypad Decoder, Front Panel

Theory of Operation Model GFC7001E Carbon Dioxide Analyzer

11.5.10.3.Display

The main display of the analyzer is a vacuum florescent display with two lines of 40 text characters each. Information is organized in the following manner (see Figure 11-17):

Mode Field: Displays the name of the analyzer’s current operating mode.

Message Field: Displays a variety of informational messages such as warning messages, operation data and response messages during interactive tasks.

Concentration Field: Displays the actual concentration of the sample gas currently being measured by the analyzer.

Keypad Definition Field: Displays the definitions for the row of keys just below the display. These definitions are dynamic, context sensitive and software driven.

11.5.10.4.Keyboard/Display Interface Electronics

Keypad Decoder

KEYBOARD

Key Press

Detect

Serial

Data

Sample LED

(Green)

Cal LED (Yellow)

Fault LED

(Red)

Status Bit	to/fromCPU
Interrupt	I
	C
	2
Keyboard

I2C Interface

I2C to Relay Board

Display Data		Display
Decoder	Controller
Parallel Data	Display Write		Display Power
			Watchdog
		Clock
			From 5 VDC

Power Supply

Optional

Maintenance

Maint.LED

Switch

2nd Lang.

Switch

2 x 40 CHAR. VACUUM FLUORESCENT DISPLAY

Beeper FRONT PANEL

Figure 11-18: Keyboard and Display Interface Block Diagram

The keyboard/display interface electronics of the GFC 7001E/EM Analyzer watches the status of the eight front panel keys, alerts the CPU when keys are depressed, translates data from parallel to serial and back and manages communications between the keyboard, the CPU and the front panel display. Except for the Keyboard interrupt status bit, all communication between the CPU and the keyboard/display is handled by way of the instrument’s I2C bus. 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.

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