siemens S7 plc

Does anyone have an S7 instruction set for dummies, how is the real time clock set on a S7 200.All help will be gratefully received. Many Thanks


Reply to
John Brindley
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Is it a subset of the S5 ? I was not even aware there was an S7 PLC out there.


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Titan (John Brindley) wrote in news:

Check doconweb at the Siemens website. Every piece of documentation for every PLC/NC control is there, including S7.

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Titan wrote in news:BVtnd.5370151$6p.867674

No, S7 is the newest one. It is a very good PLC, much, much improved over the old S5. It has been available for a few years now. S5's were good, but could be finicky when working online with them.

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I've used S7-200's but never needed the clock. Here's a snipped from the manual (should be available on the Siemens site -- happy hunting)


Read Real-Time Clock and Set Real-Time Clock The Read Real-Time Clock (TODR) instruction reads the current time and date from the hardware clock and loads it in an 8-byte Time buffer starting at address T. The Set Real-Time Clock (TODW) instruction writes the current time and date to the hardware clock, beginning at the 8-byte Time buffer address specified by T. You must code all date and time values in BCD format (for example,

16#97 for the year 1997). Figure 6-3 shows the format of the Time buffer (T). The time-of-day (TOD) clock initializes the following date and time after extended power outages or when memory has been lost: Date: 01--Jan--90 Time: 00:00:00 Day of Week: Sunday

Error conditions that set ENO = 0

0006 (indirect address) 0007 (TOD data error) Set Real-Time Clock only 000C (clock not present)
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no spam

Here's more:




Inputs/Outputs: T Data Types: Byte Operands: IB,QB, VB, MB, SMB, SB, LB, *VB, *LD, *AC

T Year: 00 to 99 T+1 Month: 01 to 12 T+2 Day: 01 to 31 T+3 Hours: 00 to 23 T+4 Minutes: 00 to 59 T+6 0 T+7 Day of Week: 0 to 7 0 disabled 1=Sunday 7=Saturday

The following is pasted from the .pdf:


The S7-200 CPU does not perform a check to verify that the day of week is correct based upon the date. Invalid dates, such as February 30, could be accepted. You should ensure that the date you enter is correct.

Do not use the TODR/TODW instruction in both the main program and in an interrupt routine. A TODR/TODW instruction in an interrupt routine that attempts to execute while another TODR/TODW instruction is in process cannot be executed. SM4.3 is set indicating that two simultaneous accesses to the clock were attempted (non-fatal error 0007).

The time-of-day clock in the S7-200 uses only the least significant two digits for the year, so for the year 2000, the year is represented as 00. The S7-200 PLC does not use the year information in any way. However, user programs that use arithmetic or compares with the year s value must take into account the two-digit representation and the change in century.

Leap year is correctly handled through year 2096.

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No Spam

The S7-200 is a micro block style PLC. Its really a replacement for the series 95 CPUs.

The S7-300 is a totally different series of CPUs and I/O is more of an S5-1xx replacement.

The S7-200 and S7-300 lines are completely incompatible with each other and use different programming software.

There is plenty of >> Does anyone have an S7 instruction set for dummies, how is the real

Reply to
Bob Peterson

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