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How to Use 40kHz PTO/PWM of MicroLogix 1100 Series B Controller
Changes made in PTO and PWM function files of MicroLogix 1100 Series B controller and RSLogix 500 version 7.2
RSLogix500 version 7.10 or lower
ML1100 Series A
PTO
OF
Signed 16-bit value : -32768~32767
OFS
(F/W generates fault when it exceeds 20000)
JF
PWM OF
OFS
RSLogix500 display
issues
Publication 1763-RM001C-EN-P - October 2009
RSLogix500 version7.2 or higher
ML1100 Series B
ML1100 Series A
The newer version of RSLogix 500 and MicroLogix 1100 Series B handles
PTO and PWM frequencies as unsigned 16-bit integer. Therefore, if an
older version of RSLogix 500 is used with MicroLogix 1100 Series B
controller or the newer version of RSLogix 500 is used with Series A
controller, there occur compatibility issues.
• RSLogix 500 display issues : Since an older version of RSLogix 500
treats PTO/PWM frequencies as signed integers, if a user uploads a
program from MicroLogix 1100 Series B controller into the software,
a negative frequency value may be displayed. For example, 40kHz
is 0x9C40 in hexadecimal. The 0x9C40 is 40000 in unsigned integer,
but -25536 in signed integer.
• Instruction issues : All the instructions in MicroLogix controller treats
integer as signed integer. Therefore, unsigned integers in PTO/PWM
function file elements need to be carefully treated when they are
used in the variables for instructions. An undesired result may be
returned or math overflow may be detected during instruction
executions. Workaround should be used such as copying PTO/PWM
frequencies to long integer before manipulation.
The difference of PTO/PWM between Series A and Series B is the
maximum output frequency. The Series A supports up to 20kHz for PTO/
PWM output frequency and the Series B supports up to 40kHz. In other
words, Series A PTO/PWM output frequency range is in signed 16-bit
range (-32768~32767) and Series B PTO/PWM output frequency range is
in unsigned 16-bit range (0~65535). For this reason, there may be a
display issue when displaying output frequency in RSLogix500. However,
since an output frequency can not be a negative value, MicroLogix 1100
controller works properly although the displayed value looks weird.
The following table summarizes possible display issues for each different
combination of a RSLogix 500 version and MicroLogix 1100 Series.
ML1100 Series B
Unsigned 16-bit value : 0~65535
(F/W generates fault when it exceeds 40000)
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