Miscellaneous Bus Signals - DEC AlphaServer 8200 Technical Manual

2.2.9 Miscellaneous Bus Signals

Several signals are required for correct system operation. They are:
TLSB_DATA_ERROR
The TLSB_DATA_ERROR signal is used to broadcast the detection of hard
and soft data errors on the data bus to other nodes.
In general, TLSB_DATA_ERROR is asserted for all data errors detected by
any node participating in the data transaction. The assertion of
TLSB_DATA_ERROR on correctable data errors can be disabled by setting
the interrupt disable bits in the TLCNR register of all nodes.
All nodes participating in a data transfer monitor TLSB_DATA_ERROR.
The <DTDE> status bit in the TLBER register is set by the node that
transmitted the data that resulted in TLSB_DATA_ERROR being as-
serted. These participating nodes must also latch the command and bank
number in the TLFADRn registers; the address should be latched if possi-
ble (required of memory nodes).
TLSB_FAULT
The TLSB_FAULT signal is used to broadcast the detection of a system fa-
tal error condition that prevents continued reliable system operation. The
assumption is that the underlying protocol of the bus has failed and that
all nodes must reset to a known state to permit the operating software to
attempt to save state and save the memory image.
All nodes monitor TLSB_FAULT and immediately abort all outstanding
transactions and reset to a known state. All bus signals are deasserted.
All interrupt and sequence counters are reset. Timeout counters are can-
celed. All node priorities are reset. Status registers are not cleared. Also
not cleared are the contents of cache and memory.
TLSB_RESET
TLSB_RESET causes a systemwide reset. All nodes begin self-test. All
state prior to the reset is lost.
TLSB_LOCKOUT
TLSB_LOCKOUT may be used by CPU nodes to avoid certain deadlock
scenarios that might otherwise occur. The use of TLSB_LOCKOUT is im-
plementation dependent.
CPU and I/O nodes monitor the TLSB_LOCKOUT signal and delay new
outgoing requests until TLSB_LOCKOUT is deasserted. I/O port nodes is-
suing a Read Bank Lock command must not delay the corresponding Write
Bank Unlock command. The delay of new requests reduces bus activity
2-24 TLSB Bus
• TLSB_DATA_ERROR — A hard or soft data error has occurred on the
data bus.
• TLSB_FAULT — A system fatal event has occurred.
• TLSB_RESET — Reset the system and initialize.
• TLSB_LOCKOUT — Lockout request to break deadlock.