User`s guide

The XMI

2.7.3 System Reset

A power-down/power-up sequence can be emulated through the use of

the XMI RESET L line, which causes the sequencing of XMI AC LO

L and XMI DC LO L in the same way as a true power-down/power-up

sequence. This allows all nodes in the system to be returned (or "reset") to

their power-up state without cycling the power supplies. The XTC power

sequencer is used to carry out the reset sequence.

A system reset is caused by:

• Software that asserts XMI RESET L by writing to IPR55, IORESET,

with an MTPR instruction. For example, the console INITIALIZE

command generates a system reset, if no argument is given, by using

this mechanism.

• Pushing the control panel Restart button. This causes the assertion of

the XMI RESET L signal.

The XTC power sequencer monitors the XMI RESET L line and drives the

XMI AC LO L, XMI DC LO L, and XMI RESET L lines. Upon detection of

an asserted XMI RESET L line, the XTC power sequencer begins the reset

sequence. If XMI RESET L is asserted while XMI AC LO L and XMI DC

LO L are deasserted, the XTC power sequencer asserts XMI AC LO L ﬁrst,

then XMI DC LO L, and ﬁnally deasserts XMI DC LO L. In response, all

XMI nodes perform self-test and initialization. When the RESET line is

deasserted, the XTC power sequencer deasserts XMI AC LO L, completing

the emulation of the power-down/power-up sequence. If the RESET line

remains asserted until after XMI DC LO L is deasserted, then all memory

nodes reset, including those with battery backup.

2.7.4 Node Reset

A single node in a system can be reset without resetting the entire system

by writing a one to the Node Reset bit (NRST) in the XMI Bus Error

of its initialization and XMI BAD L is asserted. Accessing the node during

self-test may cause a self-test failure. Software drivers that share a node

must agree in advance that a node needs to be reset and lock the selection

of that node.

The console INITIALIZE command generates a node reset if a node ID

argument is provided.

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