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11/2010

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Encoder operational mode

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

This includes microprocessor stabilization and the program for combining Coarse

and Fine channel of the encoder for getting the absolute start position. This takes

less than 0.1 seconds.

• Tracking mode:

– MCU 12 bit position register is updated from Fine Asic every 48 μs.

– The commutation program in the MCU has a compensation for the average delay caused by the

update rate, leaving a remaining jitter of less than 24 μs RMS.

•The communication jitter expressed in electrical degrees will be proportional speed and

does not reach 6 deg RMS until the speed reaches the following values:

Serial Peripheral Interface Commands

The SPI or Serial Peripheral Interface Bus is a standard interface promoted by Motorola and Microchip among

others. It consists of 4 signals:

MOSI: Master Out Slave In

MISO: Master In Slave Out

SCK: Serial Clock

CSB: Chip Select Bar (active low)

SPI BUS

The SPI bus runs full duplex and transfers multiples of 8 bits in a frame. The SPI type is the most common

(CPOL=0, CPHA=0), also known as Microwire. Data is captured on the rising edge of SCK and the output data is

changed after the falling edge of SCK.

Figure 7: SPI BUS Timing Diagram

Serial Peripheral Interface Bus (SPI) on AMT303

APPLICATION NOTES

Pole Count

4

6

8

10

12

20

Speed Limit RPM

17,361

11,574

8,681

6,944

5,787

3,472

SCK

MISO

MOSI

CSB

msb

lsb

msb

lsb

Setup

Terminology

MSB = most significant byte

LSB = least significant byte

msb = most significant bit

lsb = least significant bit

phone 503.612.2300

fax 503.612.2380 www.cui.com

AMT303

COMMUTATION ENCODER