User`s manual

Page - 63
7.0 - Troubleshooting Section
PMAC is a highly reliable device and has several safety mechanisms to prevent continuous damage and malfunctions.
When PMAC shuts-down or an erratic behavior is observed the following reset procedure should be tried.
7.1 - Resetting PMAC to factory defaults
1) If PMAC is communicating with the host computer skip steps 2-7 on this list.
2) Turn off PMAC or the host computer where PMAC is installed.
3) Remove all cables connected to PMAC only leaving connected the serial port and power cables if present.
4) Using the appropriate hardware reference for the particular PMAC in question check that all its jumpers are at the
default configuration or properly changed to accommodate the particular setup for the machine. Make sure that jumper
E50 is properly installed; otherwise any SAVE command issued to PMAC will not have any effect.
5) Place the jumper E51 in PMAC (1) or jumper E3 on PMAC2. This is a hardware re-initialization jumper.
6) After power-up try establishing communications again with a reliable software package like the PEWIN program
provided by Delta Tau.
7) On power-up, with the re-initialization jumper installed, some PMAC’s with the flash memory option will be in a mode
called “bootstrap”. This means that will accept a binary file downloaded to change its internal firmware. If this is the
case, follow the instructions on the PEWIN screen to disable the downloading process (usually pressing CTRL+R).
8) Try communications with PEWIN and type the following commands when the terminal gets successfully open (follow
the communications troubleshooting section below in case communications are still not established):
$$$*** ;Global Reset
P0..1023=0 ;Reset P-variables values
Q0..1023=0 ;Reset Q-variables values
M0..1023->* M0..1023=0 ;Reset M-variables definitions and values
UNDEFINE ALL ;Undefine Coordinate Systems
SAVE ;Save this initial, “clean”configuration
9) If the re-initialization jumper was installed remove it at this time. Restore PMAC in the computer and power it up.
10) Try communications again and configure PMAC for your application. It is strongly recommended to have a backup file
saved in the host computer with all the parameters and programs that PMAC needs to run the application. Furthermore,
since the host computer could also fail and be replaced, save the configuration file both in the host computer and in a
floppy disk stored in a safe place. This file must be downloaded and a SAVE command must be issued to PMAC.
7.2 - The watchdog timer (red LED)
The PMAC motion control board has an on-board "watchdog timer" (sometimes called a "dead-man timer" or a "get-lost
timer") circuit whose job it is to detect a number of conditions that could result in dangerous misfunction, and shut down the
card to prevent a misfunction. The philosophy behind the use of this circuit is that it is safer to have the system not operate
at all than to have it operate improperly.
Because the watchdog timer "wants" to fail, and many components of the board, both hardware and software, must be
working properly to keep it from failing, it may not be immediately obvious what the cause of a watchdog timer failure is.
The hardware circuit for the watchdog timer requires that two basic conditions be met to keep it from tripping. First, it must
see a DC voltage greater than approximately 4.75V. If the supply voltage is below this value, the circuit's relay will trip.
This prevents corruption of registers due to insufficient voltage. The second necessary condition is that the timer must see a
square wave input (provided by the PMAC software) of a frequency greater than approximately 25 Hz. If the card, for
whatever reason, due either to hardware or software problems, cannot set and clear this bit repeatedly at this frequency or
higher, the circuit's relay will trip.
Every RTI, PMAC reads the 12-bit watchdog timer register (Y register $1F) and decrements the value by 8 -- this toggles
bit 3. If the resulting value is not less than zero, it copies the result into a register that forces the bit 3 value onto the
watchdog timer. Repeated, this process provides a square-wave input to the watchdog timer.