Sources Of Local Bus Errors; Local Bus Timeout; Vmebus Access Timeout; Vmebus Berr - Motorola MVME1X7P Programmer's Reference Manual

Programming Issues
1

Sources of Local Bus Errors

Local Bus Timeout

VMEbus Access Timeout

VMEbus BERR*

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A TEA* signal (indicating a bus error) is returned to the Local Bus master
when a Local Bus time-out occurs, a DRAM parity error occurs and parity
checking is enabled, or a VME bus error occurs during a VMEbus access.
The sources of Local Bus errors on the Single Board Computers are
described in the next subsections.
A Local Bus Timeout occurs whenever a Local Bus cycle does not
complete within the programmed time (VMEbus bound cycles are not
timed by the Local Bus timer). If the system is configured properly, this
should only happen if software accesses a non-existent location within the
onboard address range.
A VMEbus Access Timeout occurs whenever a VMEbus bound transfer
does not receive a VMEbus bus grant within the programmed time. This is
usually caused by another bus master holding the bus for an excessive
period of time.
A VMEbus BERR occurs when the BERR signal line is asserted on the
VMEbus while a Local Bus master is accessing the VMEbus. VMEbus
BERR should occur only if one of the following events is detected:
An initialization routine samples to see if a device is present on the
VMEbus and it is not.
Software accesses a nonexistent device within the VMEbus range.
Erroneous configuration data causes the VMEchip2 to incorrectly
access a device on the VMEbus (such as driving LWORD low to
a 16-bit board).
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