Teledyne M300EM operation manual I2C INTERFACE CHIP, Display Data Decoder, Display Controller

Teledyne API – Technical Manual - Model 300E Family CO Analyzers Theory of Operation

I2C 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 the I2C 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 Section 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 Section 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 WATCH DOG

The M300E Analyzer’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 brownout watch dog 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

I2C LINK TO THE RELAY PCA

While the CPU’s I2C communication with the relay board is 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.

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