CD522_SSI_CNT¶
| Parameter | Value |
|---|---|
| Library_File_Name | CD522_AC500_V13.lib |
| Available from PLC runtime system: | V1.0.2 |
| Available from S500 I/O modules (DC551/DC505) firmware | V1.11 |
| Available from CD522 firmware | V2.1 |
| Type | Type_Function_Block_History |
The module CD522 can be used in 12 different configurable operating modes. The operating mode is configured in PLC Configuration using module parameters. After that, it is activated during the initialization phase (power-on, cold start, warm start).
The data exchange from and to the user program is performed using input and output operands. These necessary operands are created and reserved automatically, when one module CD522 is added into the I/O-Bus configuration.
In order to configure and use the function counter of module CD522, different operating modes are available. The Function Block CD522_SSI_CNT should be used with one of these operating modes:
| Operating Mode 14 | “SSI, absolute encoder” |
| Should be specified in PLC Configuration; parameter mode counter in order to use absolute encoder with SSI interface. | |
The module CD522 provides 2 SSI absolute encoder functions. There is an interface for absolute angle and linear encoders (displacement measurement systems).
It allows the transmission of absolute position information through a serial data transfer.
The transmission is based on synchronous serial communication. The device sends a clock signal to the encoder and synchronously,the encoder returns the positioning data from the most significant to the less significant bit.
The synchronization for a new data stream is based on time without clock pulse. This quiet time depends on the encoder.
Chronogram with data organization with the clock pulse
The resolution of the encoder device (see technical data from manufacturer) can be set with configuration, number of bits, etc. in PLC configuration, parameter SSI resolution in bit:
The trace B of module CD522 is switched as output signal (differential). On the rising edge of the signal, the sensor shifts a new value, starting from the most significant bit.
The clock frequency can be set to 200 kHz, 500 kHz, and 1 MHz Should be specified in PLC Configuration, parameter SSI frequency:
Attention
:strong:Risk of malfunctions!
The clock frequency is only an approximately value.
Do not use the clock frequency for any other purposes, e.g. time measurements.
SSI polling time definition
The complete read sequence is launched regularly by the module CD522. The interval between each sequence can be set from 1 ms to 255 ms in PLC Configuration, parameter SSI polling time:
SSI and touch/catch operation
Touch operation is valid with SSI sensor. The goal of touch operation is to synchronize sensors with the same hardware signal. In the SSI mode the management is different depending on the reading procedure is running or not.
If the reading procedure has already started while the touch signal becomes active, the reading procedure finishes normally and the last read value is stored in the touch register.
If the reading procedure has not started, the encoder is in the interval between 2 measurements. The reading procedure is started one time more and the result of the last reading is stored in the touch register.
SSI and Touch/Catch Operation: see EN_TOUCH <no title>.
Overflow Operation: see OFL <no title>.