CUI DEVICES | SERIES: AMT21 | DESCRIPTION: MODULAR ABSOLUTE ENCODER

date 08/05/2022 | page 2 of 10

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ENVIRONMENTAL

parameter

conditions/description

min

typ

max

units

operating temperature

-40

105

°C

humidity

non-condensing

85

%

vibration

10~500 Hz, 5 minute sweep, 2 hours on each XYZ

5

G

shock

3 pulses, 6 ms, 3 on each XYZ

200

G

RoHS

yes

REACH

EC 1907/2006

RS485 INTERFACE – 2 MBPS DATA RATE (A,B,C,D OPTIONS)

parameter

conditions/description

min

typ

max

units

protocol

RS485 balanced digital multi-port interface

data rate

8 data bits, no parity, 1 stop bit, asynchronous

2

Mbps

transceiver

Texas Instruments SN65HVD75

turnaround time

time before encoder responds with position

3

µs

driver differential output voltage

magnitude

load resistance = 54 Ω

1.5

2

3.3

V

RS485 INTERFACE – ADJUSTABLE DATA RATE (E,F,G,H OPTIONS)

parameter

conditions/description

min

typ

max

units

protocol

RS485 balanced digital multi-port interface

data rate3,4

8 data bits, no parity, 1 stop bit, asynchronous

115,200; 38,400; 19,200; 9,600

bps

transceiver

Texas Instruments SN65HVD72

turnaround time

time before encoder responds with position

115,200 bps

38,400 bps

19,200 bps

9,600 bps

10.8

30

56

110

µs

µs

µs

µs

driver differential output voltage

magnitude

load resistance = 54 Ω

1.5

2

3.3

V

Notes:

3. Data rate configured with AMT ViewpointTM

4. Default data rate on kits is 115,200 bps.

Checksum

The AMT21 encoder uses a checksum calculation for detecting transmission errors. The upper two bits of every response from the

encoder are check bits. Those values are shown in the examples below as K1 and K0. The check bits are odd parity; K1 for the odd bits

in the response, and K0 for the even bits in the response. These check bits are not part of the position, but are used to verify its validity.

The remaining lower 14 bits are the useful data. Here is an example of how to calculate the checkbits for a 16-bit response, from a 14-bit

encoder.

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

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