WIENER, Plein & Baus GmbH
31
www.wiener-d.com
6 SPECIAL MODES OF OPERATION
For test purposes, VM-DBA may be set to operate in modes other than the default mode with
the display reflecting the states of the VME bus lines latched or stretched at the last VME
activity, and the unit responsive when addressed via VME or USB interface. The modes are
largely similar to those offered by the predecessor module VDIS-2, except that they are here
controlled by internal registers rather than by front-panel switches.
There are five special modes of operation of VM-DBA, controlled by registers in the A16
address space:
1.
Raw display mode, where the states of the VME bus lines are directly mapped onto
the LED display, i.e., without being latched or stretched.
2.
Pseudo-DTACK mode, where VM-DBA generates a DTACK signal after
determining that such has not been issued within a user-defined timeout window.
3.
Halt-enabled mode, when the LED display of VM-DBA freezes at the detection of
BERR, requiring a reset to re-activate the display.
4.
IRQ-enabled mode, where VM-DBA generates an IRQ upon detecting a valid IRQ
trigger. Subsequently VM-DBA handles the whole IRQ cycle.
5.
Passive mode, where response of VM-DBA to VME commands is suppressed, with
the exception of an unlocking sequence
The modes are reasonably non-exclusive with the exception of the passive mode, when VM-
DBA is nonresponsive to conventional commands.
The modes are controlled by 3 D32-mode registers in the A16 address space, the Control
Register 1, Interrupt control register, and interrupt software trigger register. The structure of
these registers is illustrated in tables below.
Control Register 1 at the base address of 0 (A16 mode)
Bits
6
5
2
0
Function
PASSIVE
RAW
HENA
PDTACK
LED label
PASS
CONT
H
VD-E
Interrupt Control Register at the base address of 16 (0x10) (A16 mode)
Bits
15,14
13,12
10 - 8
7 - 0
Function
IRQTRSEL
TOUT
IRQ-ID
IRQVECT
LED label
I-EN
-
-
-
IRQTRSEL – IRQ trigger selection code:
0 – IRQ facility disabled
1 – IN (NIM/TTL)
