Pni MS2100 User Manual download pdf (Page 9)

PNI Sensor Corporation 133 Aviation Blvd., Suite 101, Santa Rosa, CA 95403-1084 USA;, Fax: (707) 566-2261

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21-Jan-11 Page 9 of 16-

MS2100

Specifications & Instructions

SPI Port Usage Tips

A SPI port can be implemented using different clock polarity options. The clock polarity used with the

MS2100 must be normally low, (cpol = 0). Figure 3 graphically shows the timing sequence (cpol = 0).

Data is always considered valid while the SCLK is high (t

DASH

= Time, Data After SCLK High). When

SCLK is low, the data is in transition (t

DBSH

= Time, Data Before SCLK High).

When implementing a SPI port, whether it is a dedicated hardware peripheral port, or a software

implemented port using general purpose I/O (also known as Bit-Banging) the timing parameters given in

Figure 3 must be met to ensure reliable communications. The clock set-up and hold times, t

DBSH

and

DASH

must be greater than 100 nS.

Idle Mode

The MS2100 does not initialize in the idle mode at power-up. The MS2100 must be in a data-

ready state for the idle mode to occur. After power-up the MS2100 can be brought to the data-

ready state by following these steps for sending a read command to the MS2100.

1. Set SSNOT low.

2. Pulse the RESET line.

3. Send a command to the MS2100 to measure one of the sensors.

4. Once the SSNOT pin is set to high again the MS2100 will go into the low power idle

mode.

5. The DRDY pin will eventually go high signifying that the MS2100 is in the data-ready

state. The resultant data does not have to be read from the MS2100.

Magnetic Measurements

The MS2100 magnetic sensor operates as an oscillator circuit composed of the internal sensors, bias

resistors, digital gates and a comparator. Only one sensor can be measured at a time. The user sends a

command byte to the MS2100 through the SPI port specifying the sensor axis to be measured. After

dividing by the ratio set by PS2-PS0, the MS2100 will return the result of a complete forward - reverse

measurement of the sensor in a 16-bit 2’s complement format (Range: -32768 to 32767)

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Pni MS2100 User Manual Page 9