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date 12/14/2018

│ page 2 of 9

CUI Inc

│ SERIES: AMT22 │ DESCRIPTION: MODULAR ABSOLUTE ENCODER

SERIAL INTERFACE

parameter

conditions/description

min

typ

max

units

protocol

Serial Peripheral Interface Mode 0

frame size

8

bit

data rate

2

MHz

transceiver

T

CLK

1500

ns

T

B

time between bytes

2.5

µs

T

CS

time between reads

TBD

µs

Notes:

1. See Microchip documentation for more details.

2. This is the time it takes to load the most current position into the SPI buffer which prevents multiple read/response commands from being required.

1

K1

K0

D14

D13

D12

D11

D10

D9

CHIP SELECT

SCLK

MISO

1

First Command Char

T

CS

C7

C6

C5

C4

MOSI

23

4

5

6

7

8

C3

C2

C1

C0

D8

D7

D6

D5

D4

D3

D2

D1

C7

C6

C5

C4

C3

C2

C1

C1

T

CLK

T

B

23

4

5

6

7

8

Second Command Char

Figure 1

Timing Waveform

Values K1 and K0 in the response are checkbits. The checkbits are odd parity over the odd and even bits in the position

response shown in the equation below. The checkbits are not part of the position, but are used to verify its validity. The

lower 14 bits are the encoder position.

Example:

Full response: 0x61AB

14-bit position: 0x21AB (8619 decimal)

Checkbit Formula

Odd: K1 = !(H5^H3^H1^L7^L5^L3^L1)

Even: K0 = !(H4^H2^H0^L6^L4^L2^L0)

From the above response 0x61AB:

Odd: 0 = !(1^0^0^1^1^1^1) = correct

Even: 1 = !(0^0^1^0^0^0^1) = correct

For 12-bit applications L0 and L1 are always 0. Because the low two bits are 0, 12-bit data will need right-shifted two bits.

The checkbit calculation remains the same and unaffected.

For more information, please visit the product page.