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ANALOG BIT BOMB

by Tom Cantrell

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BANK HEIST

The final piece of the pie is a built-in controller that handles the SPI interface, process commands (see Table 2), and performs various housekeeping tasks.

Because precision is the name of the game, the ý1216 offers various calibration commands that can be performed after power-on and periodically as necessary to compensate for temperature drift, sensor aging, and such. The self-calibration commands are handled internally by the ý1216, and the system-calibration commands encompass external circuitry as well. For calibrating system offset, the external analog input must be set to 0, and for system gain, set to full scale.

A particular ý1216 configuration is defined by the contents of 16 registers. With eight input channels available, itýs conceivable that a different configuration may be desired for each. Instead of the host micro having to keep track of them all and swap back and forth, the ý1216 includes eight banks of RAM (see Figure 5) and commands to copy a bank to or from the registers in one fell swoop. There are also commands to calculate the checksum for the register and RAM banks, just to be sure nothing has gone awry.

Figure 5ýEight banks of RAM and bank-level copy commands facilitate channel-specific configuration. Any banks not needed for that purpose can be used as general-purpose RAM in a pinch.

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