A31316 datasheet(29/61 Pages) ALLEGRO

29 / 61 page

3D Magnetic Position Sensor IC

A31316

Allegro MicroSystems

955 Perimeter Road

Manchester, NH 03103-3353 U.S.A.

www.allegromicro.com

Optional SENT Slow Serial Output Protocol

SENT output supports an optional mode to transmit additional

data. The slow serial mode enables transmission of additional

data by encoding information in the Status and Communication

(SCN) nibbles. The encoded data is captured over several trans-

missions and is then decoded to indicate additional serial message

data. For more details on the serial message, refer to the SENT

SAE J2716 APRIL2016 specification.

The slow serial mode is enabled when the EEPROM parameter

sent_emsg_dis = 0. Following a reset, the first message trans-

mitted is 0, following in order of the message ID until message

7, and then repeating. Table 19 and Table 20 identify the data

sent with each message ID. The CRC for the Serial Message is

derived from the Message ID and data.

Table 13: SCN [3:2] Configuration Control

sent_emsg_dis SCN Nibble bits [3:2] Contents

Serial Message

All Zeros

The data in the serial message follows the table below:

Table 14: Serial Message Format in SENT Status and Communication Nibble

received SCN nibble #

SCN[3]

8-bit ID[7:4]

8-bit ID[3:0]

SCN[2]

6-bit CRC

12-bit data field

There are a number of codes available to be sent out in serial

mode.

Some codes are based on sensor data, such as the following:

$01:

Error and Status Codes

$23:

Supplementarydatachannel#4,1(Temperature

data)

Other codes only send out constants, such as:

$03:

Channel 1 / 2 Sensor type

$05:

Manufacturer code

$06:

Protocol standard revision

$07-0A:

Fast Channel 1 Characteristic X1, X2, Y1, Y2

$29~2C:

Sensor ID #1~4

$90~97:

ASCII character OEM codes MESSAGE ID

Due to EEPROM sharing, the constant values are not compatible

with all Linearization modes. The constant values are factory-

programmed to EEPROM locations that are shared with for

lin_coeff_17 through lin_coeff_31. If using linearization in paral-

lel with these constants, only lin_coeff_00 through lin_coeff_16

should be used. This means fixed position linearization and

binning can be used with up to 17 points, and variable segment

linearization and binning can be used with up to 6 points. See

Table 8 for reference. For selecting how many coefficients are

used, see Table 9 for the desired coeff_active setting.

If the lin_coeff_xx value that is assigned to a constant is changed,

the new value will be output instead of the desired constant. For

that reason, it is important to take caution when programming

linearization coefficients, to ensure desired constant values are

not overwritten.

Each message can be activated or deactivated using the sent_

emsg_sel EEPROM bits. In this way, if the first constant(s)

is(are) not required, their corresponding lin_coeff_xx value(s)

can be used for linearization. The lowest $xx value used deter-

mines how many extra linearization coefficients can be used. If

$03 is used, even if no other constants are reported, only 17 or 6

coefficients can be used for fixed or movable point respectively

(e.g. if constant $03 and $05 are not reported, up to 19 fixed point

coefficients or 8 movable point coefficients can be used).

Using the EEPROM setting sent_serial_repeat_1 = 1, the

message-ID $01 is repeated between any other messages. That

means that if messages $01, $07, $08, $09, $0A are activated,

transmission will be $01-$07-$01-$08-$01-$09-$01-$0A-$01-

$07-$01-$08-….

The tables below give the serial output message numbers, the

enable bits, the data source, and the byte contents.

A31316 Datasheet(PDF) 29 Page - Allegro MicroSystems

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