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Operating Instructions
Software Initialization
Most functions that have been done with switches or jumpers on other modules are
done by setting control registers on the MVME167. At powerup or reset, the EPROMs
3
that contain the 167Bug debugging package set up the default values of many of these
registers.
Specific programming details may be determined by study of the MC68040
Microprocessor User's Manual. Then check the details of all the MVME167 onboard
registers as given in the MVME166/MVME167/MVME187 Single Board Computers
Programmer's Reference Guide.
Multi-MPU Programming Considerations
Good programming practice dictates that only one MPU at a time have control of the
MVME167 control registers.
Of particular note are:
registers that modify the address map;
registers that require two cycles to access; and
VMEbus interrupt request registers.
Local Reset Operation
Local reset (LRST) is a subset of system reset (SRST). Local reset can be generated
five ways: expiration of the watchdog timer, pressing the front panel RESET switch (if
the system controller function is disabled), by asserting a bit in the board control
register in the GCSR, by SYSRESET*, or by powerup reset.
N
ote
Any VMEbus access to the MVME167 while it is in the reset state is ignored. If a
global bus timer is enabled, a bus error is generated.
3-30
The GCSR allows a VMEbus master to reset the local bus. This
feature is very dangerous and should be used with caution. The
local reset feature is a partial system reset, not a complete
system reset such as powerup reset or SYSRESET*. When the
local bus reset signal is asserted, a local bus cycle may be
aborted. The VMEchip2 is connected to both the local bus and
the VMEbus and if the aborted cycle is bound for the VMEbus,
erratic operation may result. Communications between the local
processor and a VMEbus master should use interrupts or
mailbox locations; reset should not be used in normal
communications. Reset should be used only when the local
processor is halted or the local bus is hung and reset is the last
resort.
MVME167 Single Board Computer User's Manual
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