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Siemens POS INPUT, Reference Manual

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Siemens POS INPUT Reference Manual Download Page 17

17

Product Information on the Reference Manual Programmable Logic Controllers S7-300 Module Data Release 3
A5E00409892-01

1.1.7

Technical Specifications of the 338; POS-INPUT

Dimensions and Weight

Dimensions  B x H x T
(mm)

40 x 125 x 120

Weight

Approx. 235 g

Voltages, Currents, Potentials

Rated load voltage L+

•

Range

•

Reverse polarity
protection

24 VDC

20.4 ... 28.8 V

No

Isolation

no, only against shield

Permitted potential
difference

•

between input 
(M connection) and
central grounding point
of the CPU

 

1 VDC

Encoder supply

•

Output voltage

•

Output current

L+ –0.8 V

max. 900 mA, short
circuit–proof

Current dissipation

•

From the backplane
bus

•

From the load voltage
L+ (no load)

max. 160 mA

max. 10 mA

Power dissipation of the
module

typ. 3 W

Encoder inputs POS INPUT 0 to 2

Position decoding

absolute

Difference signals for SSI
data and SSI clock

according to RS422

Data transfer rate and cable
length of absolute value
encoders (twisted pair and
shielded)

•

125 kHz max. 320 m

•

250 kHz max. 160 m

•

500 kHz max. 60 m

•

   1 MHz max. 20 m

Message duration of the 
SSI transmission

•

125 kHz

•

250 kHz

•

500 kHz

•

1 MHz

13 bits     21 bits     25 bits  
 

112 

m

s    176  

m

s   208  

m

s

 56 

m

s      88  

m

s    104  

m

s

 28  

m

s      44  

m

s      52  

m

s

 14  

m

s      22  

m

s      26  

m

s

Monoflop time

2

16 

m

s, 32  

m

s, 48  

m

s, 64  

m

s

Digital inputs DI 0, DI 1

Isolation

no, only against shield

Input voltage

0-Signal: –3 V ... 5 V

1-Signal: 11 V ... 30.2 V

Input current

0-Signal: 

v

2 mA

(quiescent current)

1-Signal: 9 mA (typ.)

Input delay

0 > 1: max. 300 

m

s

1 > 0: max. 300 

m

s

Maximum repeat frequency

1 kHz

Connection of a two–wire
BEROS, type 2

Possible

Shielded line length

600 m

Unshielded line length

32 m

Status, Interrupts, Diagnostics

Interrupts

•

Diagnostic interrupt

Parameters can be
assigned

Status display of digital
inputs

Group error/fault

LED (green)

LED (red)

Inaccuracy of the encoder value

Free running encoder value acquisition 
(Standard Mode)

•

Maximum age 

1)

(2 

×

 Message duration)

+ monoflop time
+ 580 

m

s

•

Minimum age 

1)

Message duration
+ 130 

m

s

•

Jitter

Message duration
+ monoflop time
+ 450 

m

s

Update rate

Evaluation of the message
every 450 

m

s

Free–wheeling sensor value detection (Fast  Mode)

•

Maximum age 

1)

(2 

×

 

Message duration)

+ monoflop time

 + 400 

m

s

•

Minimum age 

1)

Message duration

+

100 

m

s

•

Jitter

Message duration

+

monoflop time

 + 360 

m

s

Update rate

Evaluation of the message
every 360 

m

s

Synchronous encoder value acquisition

•

Age

Encoder value at time T

i

 of

the current PROFIBUS DP
cycle

Summary of Contents for POS INPUT

Page 1: ...mum three absolute value encoders SSI and 2 digital inputs to freeze the encoder values Direct reaction possible to encoder values in moving systems Processing of acquired encoder values of the SM 338 in user program Supports clocked operation Type of encoder value acquisition see chapter 1 1 2 1 can be selected Free running Clocked 24 VDC rated input voltage Non isolated against the CPU Fast mode...

Page 2: ...ts the gray code and binary code data formats Firmware update1 You can use STEP 7 HW Config firmware update to load POS INPUT in the operating system memory of the SM 338 in order to extend the functionality and trouble shooting Note The old firmware is deleted with the start of the firmware update If the firmware update is interrupted or canceled for any reason the SM 338 POS INPUT is no longer f...

Page 3: ...interface IM 153 x which supports synchronous operation Characteristics Depending on the system parameterization the SM 338 works in either non synchronous or synchronous mode In synchronous operation the data exchange between DP master and SM 338 is synchronous to the PROFIBUS DP cycle In synchronous operation all 16 bytes of the checkback interface are consistent If synchronicity is lost due to ...

Page 4: ...gic M RS 422 Twisted pair cables DI 0 DI 1 Connection to the ground of the CPU Figure 1 1 Module View and Block Diagram of the SM 338 POS INPUT Wiring rules Please observe the following important rules of the wiring of the module The ground of the encoder supply is connected non isolated to the ground of the CPU Thus connect pin 2 of the SM 338 M with low impedance with the ground of the CPU The e...

Page 5: ... transfer of a message after the end of the parameterized monoflop time Asynchronous to these free running messages the SM 338 processes the acquired encoder values during the cycle of its updating rate see Technical Data Thus in the case of free running encoder value acquisition encoder values of different ages result The difference between the maximum and minimum age is the jitter see Technical ...

Page 6: ...ed before and after the encoder position are also transferred in addition to the encoder position So that the SM 338 can detect the encoder position make the following settings Normalization places 0 12 or Normalization units revolution Normalization places The normalization determines the position of the encoder values in the checkback interface If Places 1 2 12 this indicates that the following ...

Page 7: ... 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 1 0 0 0 0 0 0 0 0 Relevant bits Double data word Double data word Result Bits 0 to 3 4 places marked with x are omitted 1 1 2 4 Freeze Function The freeze function freezes the current encoder values of the SM 338 The freeze function is coupled to the digital inputs DI 0 and DI 1 of the SM 338 The freeze is triggered by an edge change rising edge o...

Page 8: ... address of the module In synchronous operation the acknowledgment is processed at time To From this point in time a renewed freezing of the encoder values can take place via the digital inputs Warning The freeze function is automatically acknowledged if you newly parameterize the corresponding channel with different parameters see 1 1 3 chapter If the parameters remain identical the freeze functi...

Page 9: ...lop time must always be greater than the monoflop time of the absolute value encoder Normalization Places Units revolution 4 0 to 12 2 to 8192 Normalizing right justifies the encoder values of the encoder absolute non relevant places are discarded Switching on freeze off 0 1 Designation of the digital input whose rising edge causes a freezing of the encoder value 1 See technical data of the absolu...

Page 10: ...TEP 7 Input Addresses Table 1 2 SM 338 POS INPUT Input Addresses Encoder input Input address from the configuration address offset 0 Initial module address 1 Module start address 4 bytes address offset 2 Module start address 8 bytes address offset Structure of the double data word in Standard Mode For each encoder input the double data word is made up as follows Freeze 0 encoder value is not froze...

Page 11: ...tus of the I0 is set in bit 27 status digital input and in the double data word of channel 1 the status of the digital input I1 is set The bit is always 0 in the double data word of channel 2 Output Address im Standard Mode Acknowledging the freeze function Bit 0 encoder input 0 Bit 1 encoder input 1 Bit 2 encoder input 2 Initial module address 0 7 Reading out data areas You can read out the data ...

Page 12: ...ze status for later acknowledgment Read encoder value in the address range for encoder input 1 Store encoder value in marker double word Acquire and store freeze status for later acknowledgment Read encoder value in the address range for encoder input 2 Store encoder value in marker double word Acquire and store freeze status for later acknowledgment Load and acknowledge freeze condition SM 338 ou...

Page 13: ...stic interrupt is triggered and OB 82 is called Reading out diagnostic messages You can read out detailed diagnostic messages by means of SFCs in the user program refer to the Appendix Diagnostic Data of Signal Modules You can view the cause of the error in STEP 7 in the module diagnosis refer to online Help for STEP 7 Diagnostic message via SF LED The SM 338 indicate errors for you by means of th...

Page 14: ...essage LED Scope of the Diagno stics Module problem SF Module Internal malfunction SF Module External malfunction SF Module Channel error present SF Module External auxiliary supply missing SF Module Module not parameterized SF Module Wrong parameters SF Module Channel information available SF Module Time monitoring triggered SF Module Channel error present SF Channel encoder input Configuring par...

Page 15: ...arameterized Module requires information whether it should work with parameters preset by the system or with your parameters Message present after network active until transfer of the parameters by the CPU complete parameterize module if necessary Wrong parameters One parameter or the combination of parameters is not plausible Reassign module parameter Channel information present Channel error pre...

Page 16: ...ut appropriate parameter assignment Assign parameters to the Interrupt Enable in STEP 7 refer to Section 1 1 3 Diagnostic interrupt If you have enabled diagnostic interrupts then incoming active error events initial occurrence of the error and departing error events message after troubleshooting are reported by means of interrupts The CPU interrupts execution of the user program and processes the ...

Page 17: ...z 1 MHz 13 bits 21 bits 25 bits 112 ms 176 ms 208 ms 56 ms 88 ms 104 ms 28 ms 44 ms 52 ms 14 ms 22 ms 26 ms Monoflop time2 16 ms 32 ms 48 ms 64 ms Digital inputs DI 0 DI 1 Isolation no only against shield Input voltage 0 Signal 3 V 5 V 1 Signal 11 V 30 2 V Input current 0 Signal v2 mA quiescent current 1 Signal 9 mA typ Input delay 0 1 max 300 ms 1 0 max 300 ms Maximum repeat frequency 1 kHz Conne...

Page 18: ...onoflop time 450 ms Synchronous encoder value acquisition Jitter Max message durationn param Monoflop time n n 0 1 2 Channel Isochrone time of the module In Standard Mode TWE 850 ms TWA 620 ms ToiMin 90 ms TDPMin 1620 ms In Fast Mode TWE 700 ms TWA 0 ms ToiMin 0 ms TDPMin 900 ms 1 Age of the encoder values determined by the transfer process and the processing 2 The following restriction applies to...

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