MA800 – 8-BIT, DIGITAL ANGLE SENSOR

MA800 Rev. 1.02

www.MonolithicPower.com

14

6/15/2018

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SPI Write Register

Table 7 shows the programmable 8-bit registers.

Data written to these registers are stored in the

on-chip non-volatile memory and reloaded

during power-on automatically. The factory

default register values are shown in Table 8.

A write register operation is constituted of two

16-bit frames. The first frame sends a write

request,

which

contains

the

3-bit

write

command (100) followed by the 5-bit register

address and the 8-bit value (MSB first). The

second frame returns the newly written register

value (acknowledge).

The on-chip memory is guaranteed to endure

1,000 write cycles at 25°C.

It is critical to wait 20ms between the first and

second frame. This is the time taken to write the

non-volatile memory. Failure to implement this

wait period results in the register

’s previous

value being read. Note that this delay is only

required after a write request. A read register

request and read angle do not require this wait

time.

The first 16-bit SPI frame (write request) is:

MSB

LSB

MISO

Angle(15:0)

command

reg. address

reg. value

MOSI

1

0

0

A4 A3 A2 A1 A0 V7 V6 V5 V4 V3 V2 V1 V0

The second 16-bit SPI frame (response) is:

reg. value

MISO V7 V6 V5 V4 V3 V2 V1 V0

0 0 0 0 0 0 0 0

MSB

LSB

MOSI

0

The read-back register content can be used to

verify the register programming. See Figure 13

for a complete transmission overview.

For example, to set the value of the output

rotation direction (RD) to counterclockwise

(high), write register 9 by sending the following

first frame:

MSB

LSB

MISO

Angle(15:0)

command

reg. address

reg. value

MOSI

1

0

0

0

1

0

0

1

1 0 0 0 0 0 0 0

Send the second frame after 20ms of wait time

(see Figure 8). If the register is written correctly,

the reply is:

reg. value

MISO 1 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

MSB

LSB

MOSI

0

See Figure 14 for a complete example.

Figure 13: Overview of Two 16-Bit Frames Write Register Operation