AMM5A & AMM5B • SSI, BiSS, & RS-485
6.2 Single Cycle Data SCD
6.2.1 SCD structure
SCD data has a variable length according to the resolution of the encoder. It is
7 long where “nbitres” is the resolution of the encoder expressed in bits.
It consists of the following elements: position value (
), 1 error bit nE
) and a 6-bit CRC Cyclic Redundancy Check
).
bit
7 … 8
7
6
5 … 0
function
Position
(Nbitres)
It is the process data transmitted from the Slave to the Master. It has a variable
length, it is as long as the resolution of the encoder expressed in bits.
The transmission starts with msb (most significant bit) and ends with lsb (least
significant bit). “Nbitres” is the resolution of the encoder expressed in bits.
bit
7
...
...
8
value
msb
...
...
lsb
“Nbitres” is the resolution of the encoder expressed in bits. It is comprised
between 17 bits and 39 bits a shown in the following table.
Order code
Encoder resolution
AMM5A17/1SC1...
AMM5B17/1SC1...
17 bits
AMM5A21/1SC1...
AMM5B21/1SC1...
21 bits
AMM5A23/1SC1...
AMM5B23/1SC1...
23 bits
AMM5A17/65KSC1...
AMM5B17/65KSC1...
17 + 16 bits
AMM5A21/65KSC1...
AMM5B21/65KSC1...
21 + 16 bits
AMM5A23/65KSC1...
AMM5B23/65KSC1...
23 + 16 bits
Error
(1 bit)
It is intended to communicate the normal or fault status of the Slave.
When nE = “0” (low active), an error is active in the system.
1. It indicates that an error is active, such as for instance an incorrect
alignment between the circuitry and the disk:
MAN AMM5A_B SSI_BiSS_RS485 E 1.9.odt
6 - BiSS C-mode interface
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