WIENER, Plein & Baus GmbH
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9 IRQ SERVICE TEST
VM-DBA allows one to test the integrity of the IRQ handling net in the VME crate by
issuing, upon detecting a valid trigger signal, an IRQ on any of the seven IRQ1 – IRQ7 lines.
Subsequently it responds to the IAQ/IAQIN/AS inquiry by the IRQ handler by placing on
VME bus data lines 0 – 7 a preprogrammed IRQ vector accompanied shortly after by
DTACK. This IRQ vector is assumed to be recognizable to the IRQ handler, which after
terminating the IRQ handshaking cycle performs the duty assigned to this particular IRQ ID
and this particular IRQ vector.
VM-DBA implements two modes of IRQ resetting, RORA (Reset on Register Access) and
ROAC (Reset on Access). The RORA mode requires the VME controller to reset IRQ by
writing 2 into Software Interrupt Register at A16 base address of 32 (0x20). When
configured for ROAC mode, VM-DBA resets IRQ upon detecting valid IRQ vector on VME
Bus address lines 1-3, accompanied by AS, IACK, and IACKIN.
Setting up the IRQ testing involves writing into the IRQ register at the A16 address offset of
16 (0x10) the IRQ setup word structured as shown in table below
Structure of the IRQ setup word
Bits
14, 15
12, 13
11
8 - 10
0 - 7
Function TrigSel
TOUT
ROAC
IRQID IRQVECT
IRQVECT - 8-bit IRQ vector identifying the requestor VM-DBA to the IRQ handler
IRQID – 3-bit code identifying the IRQ bus line 1 – 7
ROAC – when 1, ROAC mode is selected. Otherwise RORA
TOUT – unrelated to the IRQ facility time-out code described in Section 6.
TrigSel – IRQ trigger selection code
0 – IRQ generation disabled
1 – NIM/TTL
2 – Software
3 – Periodic at 1 kHz.
