PPC7A Product Manual
Functional Description
8-17
1
st
Edition
VMEbus Retries
The Universe II chip, as a PCI target, retries the PCI master under the following conditions:
•
The PCI initiator requests a coupled cycle to the VMEbus whilst the Universe II is not VMEbus
master
•
The PCI initiator requests a coupled cycle to the VMEbus whilst the posted write FIFO still
contains data
•
The PCI initiator requests a posted write cycle when the posted write FIFO can accept no more
entries
The PPC7A
does not support the VMEbus RETRY~ signal.
VMEbus Reset Options
Several Universe II chip operating features are set at power-up or reset by surface mount jumpers. See
the VMEbus Interface Configuration section in Chapter 4 for the default options.
Watchdog Timers
The PPC7A
contains a Maxim 706 microprocessor supervisory circuit with a watchdog timer. Once
enabled, this timer must be re-triggered every 1.6 seconds or a hard reset results. The trigger control
registers is 0x82C and is enabled via Control register 0x828.
$
Note:
Once this bit is enabled as an output, software needs to write to the trigger register to keep the board
from resetting. Disabling this pin once it has been enabled does not disable the Watchdog.
The GT64260 also contains a watchdog timer. This timer has a programmable timeout interval. The
watchdog output pin needs to be enabled in the GT64260 as MPP bit 9 before the watchdog can reset the
PPC7A.
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com