s700: 300C counter

QUESTION:
Is there a sample program available for using the integrated counter in the S7 CPU 31xC?
ANSWER:
The integrated counter in the S7 CPU 31xC is controlled via the SFB 47 system function block.
In addition to the inputs for controlling the counter, parameters (e.g. hysteresis, comparator
value) can also be assigned to the counter via SFB 47, and the configured data can also be
scanned via this block.
Parameters are assigned to the counter via a job (job number) and the associated value. The job is
then activated. A new job or a new parameter can only be set or scanned when the previous job is
processed. When a job is finished, this is indicated via the status register.
The function block (FB 1) which is provided here makes it much easier to assign parameters to
the counter via SFB 47. The write and read jobs are initiated via initiation bits and are
automatically reset once the job is complete. The status displays can be reset via a shared input.
The function block calls SFB 47 internally. The parameters which are required for calling SFB
47 can be derived from the call parameters for FB 1.
The following call interface is available via FB 1:
Input parameters Type Description
Module_address WORD
I/O address of the counter module in hexadecimal
form, as set in the HWCONFIG (default:
W#16#300)
Channel_number INT
Number of the channel used.
The number of channels available is dependent
on the CPU
SW_Gate BOOL Controls the software gate
Enable_output BOOL Enables the output for manual control
Control_output BOOL Direct activation of the digital output
Output parameters Type Description
STS_Gate BOOL Internal gate status display
STS_Up BOOL Counting forwards

STS_Down BOOL Counting backwards
STS_Latch BOOL Latch input status display
STS_Hardware_gate BOOL Hardware gate status display
STS_Output BOOL Digital output status display
STS_Comparator BOOL
Comparison criteria are or have been met (note
the setting in the STEP 7 HWCONFIG)
STS_Overflow BOOL Overflow has occurred
STS_Underflow BOOL Underflow has occurred
STS_Zero_mark BOOL Zero-crossing has occurred
Counter_value DINT Current channel counter status
Latch_value DINT Current latch value (last measurement)
Job_error BOOL Error display in a read or write job
Error_number WORD Job error number (in "job error = 1")
Input / Output
parameters
Type Description
Reset_status BOOL
Reset the status bits for comparator, zero-
crossing, overflow and underflow
WR_Count_value BOOL "Write count value" job initiation
WR_Load_value BOOL "Write load value" job initiation
WR_Comparator_value BOOL "Write comparator value" job initiation
WR_Hysteresis BOOL "Write hysteresis" job initiation
WR_Pulse_width BOOL "Write pulse width" job initiation
WR_Job_value DINT Value for the current write job
RD_Load_value BOOL "Read current load value" job initiation
RD_Comparator_value BOOL "Read current comparator value" job initiation
RD_Hystersis BOOL "Read current hysteresis" job initiation
RD_Pulse_width BOOL "Read current pulse width" job initiation

RD_Read_value DINT Return value for the current read job
Table 1: FB1 interface description
Using the write and read jobs:
The write jobs are triggered via a "1" on the associated initiation bit (WR_). The value being
written for the activated job is transferred at the "WR_Job_value" input. Once the write job has
ended, the activation bit is reset again and the job value is defined as "0". Only one job value
may be set at a time.
Read jobs are treated identically to write jobs. The job activation is set and is then reset again by
the block once it is completed. The returned value is output at the "RD_Read_value" parameter.
The return value is designed as an input/output parameter so as to enable the value to be set to
"0" by the calling program as well.
Resetting the status bits:
A "1" at the "Reset_Status" parameter serves to reset the status displays (e.g. overflow,
underflow). Once all the status bits have been reset, the block also resets the active bit.
Error handling:
If an error occurs during a write and read job, the initiation bit is reset, and the "Job_error" bit is
set. An error code is displayed at the "Error number" output to facilitate further diagnostics. This
is dependent on the mode. The error code is identical to the error code that is output by SFB 47.
In order to find out the meanings of the error codes, refer to the online help or to the manual
mentioned below.
The job error and the error code are reset if a job is executed correctly.
Further information / Manuals:
"Programmable Logic Controller S7-300 CPU 31xC Technological Functions",
part of the documentation package, order no. 6ES7 398-8FA10-8AA, Entry ID 12429336
Download:
The attached download contains the STEP 7 project with the FB1 function block for calling SFB
47. The block is programmed and annotated in STL. However, there is no need to change the
program code in the block for a typical application. The block can be used directly in the
LAD/FBD/STL program. In addition, the only block that has to be loaded from the standard
library is SFB 47.

FBCount31xC.exe ( 304 KB )
Copy the "FBCount31xC.exe" file into a separate folder and then start the file with a double-
click. The STEP 7 project is extracted automatically and can then be opened or processed.
Runnability and test environment:
The sample program can be used on all the CPU models in the CPU 31xC compact series.
The following table lists the components which have been used to create this entry and verify the
functions described:
Test environment Version
PC platform Pentium III, 800MHz, 260 MB main memory
PC operating system Microsoft Windows XP V5.1 SP1
STEP 7 STEP 7 V5.2 SP1
Optional packages -
S7-CPU CPU 314C 2PtP (314-6BF00-0AB0)