AS5040

Data Sheet

www.austriamicrosystems.com

Revision 2.10

12 - 33

Programming Daisy Chained Devices

In Daisy Chain mode, the Prog pin is connected directly to the DO pin of the subsequent device in the chain (see

Figure 6). During programming (see section 12), a programming voltage of 7.5V must be applied to pin Prog. This

voltage level exceeds the limits for pin DO, so one of the following precautions must be made during programming:

open the connection DO Prog during programming or

add a Schottky diode between DO and Prog (Anode = DO, Cathode = Prog)

Due to the parallel connection of CLK and CSn, all connected devices may be programmed simultaneously.

Figure 6: Daisy Chain Hardware Configuration

CSn

PROG

DI

CLK

CSn

DO

CLK

CSn

DO

CLK

PROG

CSn

DO

CLK

PROG

100R

100R

1nF

1nF

GND

GND

GND

MCU

AS5040

AS5040

AS5040

Figure 7: Daisy Chain Mode Data Transfer

Even

PAR

CSn

CLK

DO

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

18

16

COF

LIN

OCF

Mag

INC

Mag

DEC

1

t

CLK FE

Angular Position Data

Status Bits

T

CLK/2

t

DO active

t

DO valid

D

2

D9

D8 D7

3

Angular Position Data

8

Incremental Outputs

Three different incremental output modes are possible with quadrature A/B being the default mode.

Figure 8 shows the two-channel quadrature as well as the step / direction incremental signal (LSB) and the direction

bit in clockwise (CW) and counter-clockwise (CCW) direction.

Quadrature A/B Output (Quad A/B Mode)

The phase shift between channel A and B indicates the direction of the magnet movement. Channel A leads channel

B at a clockwise rotation of the magnet (top view) by 90 electrical degrees. Channel B leads channel A at a counter-

clockwise rotation.

LSB Output (Step / Direction Mode)

Output LSB reflects the LSB (least significant bit) of the programmed incremental resolution (OTP Register Bit Div0,

Div1). Output Dir provides information about the rotational direction of the magnet, which may be placed above or

below the device (1=clockwise; 0=counter clockwise; top view). Dir is updated with every LSB change.

In both modes (quad A/B, step/direction) the resolution and the index output are user programmable. The index pulse

indicates the zero position and is by default one angular step (1LSB) wide. However, it can be set to three LSBs by

programming the Index-bit of the OTP register accordingly (see Table 6).