AS8501 - Data Sheet

austriamicrosystems

Revision 1.1, 04-April-06

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After that the circuit returns in power-down for approximately 1s. During this time the last measurement (MSR register) is available on the SDI interface.

In this intermediate sleep-mode all modules except internal oscillator and divider are in power-down mode. The SDI interface works independent which

means that the measurement result is available by reading the MSR register. At any time the microprocessor can start any other mode via SDI. In such

a case the external clock must be switched on first.

The chip goes in MWU mode (mode 3) after it received the command for that. After that command 6 or more additional CLK pulses are needed before

external clock may go to power down mode (no CLK pulses, high level because of internal pull-up resistors). This 6 CLK pulses are needed for

synchronisation. On the way back to normal mode this restriction is not needed.

Mode 4: MAM

In this alarm mode the measurement defined in CRA is going on. The channel bit in the THR register must be cleared (channel A). The threshold value

may be positive or negative. Whenever the measured value exceeds the digital threshold value in the THR register the pin INTN (in this mode its

function is to signal alarm-condition) goes LO for one clock cycle. For negative threshold value the signed measurement result must be more negative

than the THR value to activate the alarm. During measurements the signal INTN is high. All modules are in power-up, measurements are continuously

going on.

Mode 5: MZP

Zener-Zap programming/reading. This mode for factory programming only and should not be used by the customer.

Mode 6: MPD

Power down mode. Individual analog blocks can be disabled/enabled. The data acquisition system is not running during this mode is activated.

Mode 7: MSI

The operation in this mode is exactly the same as in MMS mode except that the internal clock is used.

The SDI interface signals can become active whenever appropriate. This mode can be used if no external clock CLK is available. The measuring speed

is reduced by a factor of 16.

Modes 8-15: These modes are reserved for testing purposes and should not be used by the customer. Reading and writing of some registers is only

possible in these higher modes. Write to registers CAR (calibration register) and TRR (trimming register) is allowed only in test modes.