SSI parameters

The parameters of the SSI interface can be found in the CoE objects

0x8000 "SSI Settings"
0x800D "SSI Advanced Settings"

SSI settings

Index 0x8000:01, disable frame error
If the bit is set to TRUE, data errors such as invalid telegram size are no longer shown in the Data error process data.
Index 0x8000:02, enable power failure bit
If the bit is set to TRUE, the last bit (LSB) in the SSI telegram is interpreted as PowerFail bit of the SSI slave and shown in the process data.
Index 0x8000:03, enable inhibit time
If the bit is set to TRUE, the system waits at least until the Min. Inhibit time (index 0x8000:13) has elapsed when the next SSI communication starts, even if the next start request has already been issued via EtherCAT or distributed clocks.
Index 0x8000:04, enable test mode
Only for production purposes.
Index 0x8000:06, SSI-encoding
Dual or gray coding setting (standard).
Index 0x8000:09, SSI baud rate
should be set to 125, 250, 500 kbaud (default) or 1 Mbaud.
Index 0x8000:0F, SSI-frame type
25, 13 or variable bit width (default: 25).
Index 0x8000:11, SSI-frame size
Total data volume including PowerFail bit.
Index 0x8000:12, SSI-data length
Data volume without PowerFail bit.
Index 0x8000:13, Min. inhibit time [µs]
See index 0x8000:03.

SSI advanced settings

Index 0x800D:01, Encoder power supply on
Switches the 24 V supply voltage
Index 0x800D:02, Encoder direction pin on
Switches the 24 V supply at the Direction pin
Index 0x800D:03, Encoder reset pin on
Switches the 24 V supply at the Reset pin

The total size of the data depends on the encoder used. It is also type-specific whether a power-fail bit or another auxiliary bit is supported. The counter value in the Counter Value index 0x6000:11 is determined based on the value entered in object SSI data length index 0x8000:12.
A few example configurations are shown below:

Specification of the encoder			Settings in the CoE of the box
ST	MT	Error bit	0x8000:0F SSI frame type	0x8000:11 SSI frame size	0x8000:12 SSI data length	0x8000:02 Enable power failure bit
13	0	0	1: Single-turn analysis is active	13	13	0: Power failure bit is not active
12	12	1	0: Multi-turn analysis is active	25	24	1: Power failure bit is active
12	12	0	2: Variable analysis is active	24	24	0: Power failure bit is not active
12	13	0	2: Variable analysis is active	25	25	0: Power failure bit is not active
16	16	0	2: Variable analysis is active	32	32	0: Power failure bit is not active
16	0	0	2: Variable analysis is active	16	16	0: Power failure bit is not active
13	16	1	2: Variable analysis is active	30	29	1: Power failure bit is active
12	12	2	2: Variable analysis is active	26*	26*	0: Power failure bit is not active

*) Analysis of the data and division into position and auxiliary bits must take place in the PLC.

If the encoder offers more than 1 auxiliary bit, this can be done by means of suitable configuration of the objects 0x8000:11 SSI frame size and 0x80n0 SSI data length. The maximum size of 32 bits must be considered here. If the parameters have the same size, the Counter Value index 0x6000:11 does not only show the position, but also additional bits. Analysis of the data and division into position and auxiliary bits must take place in the PLC.

If the settings are not made correctly in the CoE, or if there is an error at the inputs, this is indicated via the status bits

Data error (Index 0x6000:01)	Frame error (Index 0x6000:02)	Possible error type
TRUE	FALSE	SSI input error: - SSI without power supply - Wire breakage on one of the SSI lines If no data transmission occurs, the SSI input is on low signal level.
FALSE	TRUE	There is an incorrect data frame, the data frame was not concluded with zero, or possibly - Wire breakage in the clock lines - Incorrect parameterization in the CoE
TRUE	TRUE	- Broken wire at SSI data inputs D+ or D- - Data cables interchanged
FALSE	FALSE	If bits are shifted in the counter value despite correct CoE parameterization, this may be to do with the clock lines being swapped