Local Bus Transfer Timer; Vmebus Interrupt Handling - DEC Digital Alpha VME 4/224 User Manual

Table 10–9 (Cont.) VMEbus Transfer Timeout Register
Field Name
<7:5> VMEbus
timeout

10.3.3.3 Local Bus Transfer Timer

When enabled, the local bus transfer timer starts whenever a data phase is
initiated on the local bus (the bus between the VIC64 and DC7407). If the timer
expires before the data cycle is acknowledged or terminated by an error, the
VME interface signals a local bus timeout. This condition sets a status bit in the
VMEbus error status register (VIC_BESR).

10.3.4 VMEbus Interrupt Handling

A Digital Alpha VME 4 system can act as a VMEbus interrupter as well as
a VMEbus interrupt servicing agent (as described in Chapter 11). As system
controller, the Digital Alpha VME 4 system drives the IACK daisy-chain if the
VIC64 has no VME interrupt pending.
The VIC interrupt request/status register (VME_IF_BASE + 0x80) is used to
control the state of the Digital Alpha VME 4 system's IRQ1*-7* lines driven
out onto the VMEbus. This register provides the current state of the IRQ lines.
Figure 10–14 shows the form of this register.
Description
Specifies the timeout, according to the following values:
000 4 microseconds
001 16 microseconds
010 32 microseconds
011 128 microseconds
100 256 microseconds
101 512 microseconds
111 Disabled
VME Interface 10–23