CUI DEVICES | SERIES: AMT20 | DESCRIPTION: MODULAR ABSOLUTE ENCODER

date 08/05/2022 | page 8 of 10

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APPLICATION NOTES

• Initialization mode: At power up the encoder goes through an initiation and stabilization procedure. This includes microprocessor stabilization and the

program for getting the absolute start position. This takes less than 100 milliseconds.

• Tracking mode:

1.

MCU 12 bit position register is updated from every 48

μs.

2.

For accurate position information without the 48

μs incremental outputs A/B can be used for tracking. These outputs are

operational up to 8000 RPM without speed error.

3.

When using the incremental output there also is a Z index pulse that occurs once per turn.

ENCODER OPERATIONAL MODE

The Serial Peripheral Interface (SPI) bus is a standard serial interface that operates in full duplex mode. It consists of 4 signals:

1.

MOSI: Master Out Slave In

2.

MISO: Master In Slave Out

3.

SCK: Serial Clock

4.

CSB: Chip Select (active low)

SERIAL PERIPHERAL INTERFACE COMMANDS

SCK

MISO

MOSI

CSB

MSB

LSB

MSB

LSB

Setup

The SPI bus transfers multiples of 8 bits in a frame. Data is captured on the rising edge of SCK and the output data is changed after the falling edge of

SCK.

Serial Peripheral Interface Bus (SPI) on AMT203 Timing Diagram

(Figure 1)

The data out on MISO is valid once CSB goes low. The MOSI data is valid after the falling edge of SCK. The encoder drives data out on MISO for as long as

CSB is low.

Normally, CSB goes low, then after 8 clock cycles the command is interpreted. CSB high resets the clock counter, and terminates any command

sequence.

SPI BUS

Terminology

MSB = most significant byte

LSB = least significant byte

msb = most significant bit

lsb = least significant bit

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