MA800 – 8-BIT, DIGITAL ANGLE SENSOR

MA800 Rev. 1.02

www.MonolithicPower.com

12

6/15/2018

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SPI Communication

The sensor supports three types

of

SPI

operation:

 Read angle

 Read configuration register

 Write configuration register

Each operation has a specific frame structure

described below.

SPI Read Angle

Every 1µs, new data is transferred into the

output buffer. The master device triggers the

reading by pulling CS low. When a trigger event

is detected, the data remains in the output

buffer until the CS signal is de-asserted (see

Table 4).

Table 4: Sensor Data Timing

Event

Action

CS falling edge

Start reading and freeze

output buffer

CS rising edge

Release of the output buffer

See Figure 9 for a diagram of a full SPI angle

reading. See Figure 10 for a diagram of a

partial SPI angle reading. A full angle reading

requires 16 clock pulses. The sensor MISO line

returns:

MSB

LSB

MISO

Angle(15:0)

MOSI

0

The MagAlpha family has sensors with different

features and levels of resolution. Check the

data

output

length

in

the

General

Characteristics table on page 5 for the number

of useful bits delivered at the serial output. If the

data length is smaller than 16, the rest of the

bits sent are zeros.

For example, a data output length of 12 bits

means that the serial output delivers a 12-bit

angle value with four bits of zeros padded at the

end (MISO state remains zero). If the master

sends 16 clock counts, the MagAlpha replies

with:

MSB

LSB

MISO

Angle(15:4)

0 0 0 0

MOSI

0

Therefore, angle reading can be optimized

without any loss of information by reducing the

number of clock counts. In the case of a 12-bit

data output length, only 12 clock counts are

required to get the full sensor resolution.

MSB

LSB

MISO

Angle(15:4)

MOSI

0

If less resolution is needed, the angle can be

read by sending even fewer clock counts (since

the MSB is first).

In case of a fast reading, the MagAlpha

continues sending the same data until the data

is refreshed (see the refresh rate in the General

Characteristics table on page 5).

Figure 9: Diagram of a Full 16-Bit SPI Angle

Reading

Figure 10: Diagram of a Partial 8-Bit SPI Angle

Reading