Functions; Acquisition Of Encoder Signals; Position Input With Ssi Absolute Encoder - Siemens SIMATIC S7-1500 Manual

Product overview

2.2 Functions

2.2 Functions
2.2.1

Acquisition of encoder signals

2.2.1.1

Position input with SSI absolute encoder

You can use the TM PosInput 2 technology module with an SSI absolute encoder for
position detection. The technology module reads the position via a synchronous, serial
interface from the SSI absolute encoder and sends it to the controller.
You can switch the digital outputs of the technology module exactly at defined position
values, independently of the user program. Position input with an SSI absolute encoder does
not involve gate control.
Gray-code and dual-code
Gray-code and dual-code SSI absolute encoders are supported.
Range for position value
You can specify a frame length of 10 bits to 40 bits for the SSI absolute encoder. The
configurable bit numbers of the LSB and the MSB of the position value in the frame define
the value range. The technology module can read in a position value with a maximum length
of 32 bits and transfer it to the controller.
Complete SSI frame
Instead of having a measured variable returned, you can choose to have the least significant
32 bit of the current unprocessed SSI frame returned. This provides you with encoder-
specific additional bits, such as error bits, in addition to the position value. If the SSI frame is
shorter than 32 bits, the complete SSI frame is returned right-aligned and the top unused bits
are returned with "0" in the feedback interface.
Capture (Latch)
You can configure the edge of an external reference signal that triggers saving of the current
position value as a Capture value. The following external signals can trigger the Capture
function:
● Rising or falling edge of a digital input
● Both edges of a digital input
The "Frequency of Capture function" parameter specifies whether the function is executed at
each configured edge or only once after each enable.
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Technology module TM PosInput 2 (6ES7551-1AB00-0AB0)
Manual, 06/2018, A5E03982218-AB