Command Field Parity Errors; No Acknowledge Errors - DEC AlphaServer 8200 Technical Manual

The following fields are level-checked only when the commander has won
the bus and is asserting a command and address:
A mismatch sets <ATCE> and asserts TLSB_FAULT six cycles after the
command and address. Nodes must latch the address, command, and bank
number received in the TLFADRn registers upon setting this error.
The request signals driven by the node (as determined from
TLSB_NID<2:0>) are level-checked every bus cycle. A mismatch sets
<RTCE> and asserts TLSB_FAULT four cycles after the incorrect asser-
tion.
TLSB_CMD_ACK is checked only when it is being asserted by the node. A
mismatch sets <ACKTCE> and asserts TLSB_FAULT four cycles after
TLSB_CMD_ACK should have asserted.
TLSB_ARB_SUP and TLSB_LOCKOUT are checked only when being as-
serted by the node. A mismatch sets <ABTCE> and asserts TLSB_FAULT
four cycles after the signal should have asserted.
The TLSB_BANK_AVL<15:0> signals driven by a memory node (as deter-
mined by virtual ID) are level-checked every bus cycle. A mismatch sets
<ABTCE> and asserts TLSB_FAULT four cycles after the incorrect asser-
tion.
2.4.3.2

Command Field Parity Errors

Command field parity errors result in a system fatal error and the asser-
tion of TLSB_FAULT six cycles after the command. Parity errors can re-
sult from a hardware error on the bus, a hardware error in the node send-
ing the command, from no node sending a command, or from two nodes
sending commands in the same cycle. <APE> is set in the TLBER register
if even parity is detected on the TLSB_ADR<30:5> and TLSB_ADR_PAR
signals, or if even parity is detected on the TLSB_CMD<2:0>,
TLSB_BANK_NUM<3:0>, TLSB_ADR<39:31>, TLSB_ADR<4:3>, and
TLSB_CMD_PAR signals.
Nodes latch the address, command, and bank number in the TLFARn reg-
isters upon setting this error.
2.4.3.3

No Acknowledge Errors

A commander node normally expects to receive acknowledgment to all
commands it sends on the address bus. The acknowledgment is the asser-
tion of TLSB_CMD_ACK by a slave node. There are conditions, however,
where no acknowledgment must be handled.
2-36 TLSB Bus
every cycle, enabled solely by the driven assertion value. For example,
TLSB_CMD_ACK is assertion checked to verify that if this node at-
tempts to assert it, the signal is received asserted. If this node is not
asserting TLSB_CMD_ACK, possibly some other node is asserting it.
• TLSB_ADR<39:3>
• TLSB_ADR_PAR
• TLSB_CMD<2:0>
• TLSB_CMD_PAR
• TLSB_BANK_NUM<3:0>