Iack Daisy-Chain Driver; Bus Timer; Reset Driver - Motorola MVME162FX Programmer's Reference Manual

IACK Daisy-Chain Driver

Complying with the latest revision of the VMEbus specification, the
System Controller includes an IACK Daisy-Chain Driver, ensuring
that the timing requirements of the IACK daisy-chain are satisfied.

Bus Timer

The Bus Timer is enabled/disabled by software to terminate a
VMEbus cycle by asserting BERR if any of the VMEbus data strobes
is maintained in its asserted state for longer than the programmed
time-out period. The time-out period can be set to 8, 64, or 256 secs.
The bus timer terminates an unresponded VMEbus cycle only if
both it and the system controller are enabled.
In addition to the VMEbus timer, the chip contains a local bus timer.
This timer asserts the local TEA when the local bus cycle
maintained in its asserted state for longer that the programmed
time-out period. This timer can be enabled or disabled under
software control. The time-out period can be programmed for 8, 64,
or 256 secs.

Reset Driver

The chip includes both a global and a local reset driver. When the
chip operates as the VMEbus system controller, the reset driver
provides a global system reset by asserting the VMEbus signal
SYSRESET. A SYSRESET may be generated by the
power up reset, a watch dog time-out, or by a control bit in the
LCSR. SYSRESET remains asserted for at least 200 msec, as required
by the VMEbus specification.
Similarly, the chip provides an input signal and a control bit to
initiate a local reset operation.
The local reset driver is enabled even when the chip is not the
system controller. A local reset may be generated by the
switch, a power up reset, a watch dog time-out, a VMEbus
SYSRESET, or a control bit in the GCSR.
Functional Blocks
switch, a
RESET
RESET
2-19
2