Reference Manual

Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables 57
I40 Watchdog Timer Reset Value
Range: 0 – 65,535
Units: servo cycles
Default: 0 (sets 4095)
I40 controls the value to which the watchdog timer’s counter is reset each background cycle. Each servo
interrupt cycle, Turbo PMAC decrements this counter by 1 automatically, and if the counter becomes less
than 0, the real-time interrupt task will no longer strobe the watchdog circuit, permitting it to trip and shut
down the card. Therefore, one background cycle must execute every I40 servo cycles, or the board will
shut down.
I40 permits the user to optimize the sensitivity of the watchdog timer for a particular application.
Register X:$25 contains the lowest value that the counter has reached before being reset since the last
power-on/reset.
For purposes of backward compatibility, if I40 is set to 0, Turbo PMAC will reset the watchdog timer
counter to 4095 each background cycle.
I41 I-Variable Lockout Control
Range: $0 – $F (0 – 15)
Units: none
Default: 0
I41 permits the user to lock out changes to any of several sets of I-variables in Turbo PMAC. I41 is a 4-
bit value, and each bit independently controls access to a set of I-variables. If the bit of I41 is set to 1, the
corresponding I-variables cannot be changed with an {I-variable}={value} command. The
purpose of I41 is to prevent inadvertent changes to certain I-variable values.
The following table shows the I-variable set that each bit of I41 controls.
I41 Bit #
Bit value
I-Variable Range
I-Variable Function
0
1
I100 – I4899
Motor Setup
1
2
I5100 – I6699
Coordinate System Setup
2
4
I6800 – I7999
MACRO/Servo IC Setup
3
8
I8000 – I8191
Conversion Table Setup
If there is an attempt to execute a command to set an I-variable value, either an on-line command or a
buffered program command, while the controlling bit is set to 1, the command is ignored (no error is
generated).
I41 does not prevent changes to an I-variable by means of an M-variable assignment or a direct memory
write command.
Care must be taken in downloading a complete set of I-variables with I41 at a non-zero value. Because
I41 is typically set before any of the variables it controls, if it has a non-zero value in this list, some of the
subsequent variables will not get set.
The restore function of the PEWIN32 Executive Program for 32-bit Windows operating systems Versions
2.30(?) and newer (September 1999 and later) automatically handle this situation, setting I41 to 0 at the
beginning of a download, then setting the file’s I41 value at the end of the download. Older versions of
the Executive will not perform a proper “restore” function with a non-zero value of I41.
If a Servo or MACRO IC is not present in the Turbo PMAC system, Turbo PMAC cannot set a value for
any of the setup I-variables for that IC, regardless of the setting of I41.