
VXIbus Interface
MODID / Interrupt Gen Reg MO04 MO03 MO02
MO01
MO00
Interrupt-out
8158
This register serves two purposes: driving the VXI MODID lines and generating a
VXI interrupt.
If the three low-order bits are not 000, one of the seven VXI interrupt lines is asserted
by the EPC-7. The line is the decoded value of these three bits (e.g., 001 denotes
IRQ1, 111 denotes IRQ7). If and when an interrupt acknowledge cycle is sent to the
EPC-7, the Interrupt-out bits are cleared. Software can also deassert an asserted
interrupt by clearing these bits at any time. A reset of the EPC-7 or setting bit RSTP
in the status/control register clears the Interrupt-out bits.
The MODID bits are explained in the context of the following register.
MODID Upper Register
MO12 MO11 MO10
MO09
MO08
MO07
MO06
MO05
8159
This register and the previous one drive and sample the LBUSA local bus signals on
the VXI P2 connector. When the EPC-7 is installed in slot 0, these signals are the
MODID signals on the VXI backplane. The bits named MO00-MO12 are associated
with signals MODID00-MODID12.
When a write occurs to this register (8159), the EPC-7 drives the MODID signals on
the backplane. A read of this register (8159) terminates the driving of the signals; the
value returned from this "driver-terminating" read is not specified and should not be
used. All other reads of both registers sample the MODID signals from the
backplane. A reset of the EPC-7 or setting bit RSTP in the status/control register
terminates driving of the MODID lines.
7
7
TTL
Trigger
Drive
Register
TTD7
TTD6
TTD5
TTD4
TTD3
TTD2
TTD1
TTD0
815A
This read/write register drives the VXI TTL trigger lines; a 1 bit causes the associated
trigger line to be asserted. The actual change in state to the trigger lines is synchro-
nized to the 10 MHz CLK10 to support the VXI trigger start/stop protocol. Reading
this register does not sample the triggers; it simply returns what was previously stored
in this register. Sampling the trigger lines is performed with register 8156.
A reset of the EPC-7 clears this register.
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