Nonacknowledged Csr Reads; Address Bus Errors - DEC AlphaServer 8200 Technical Manual

3.5.1.4

Nonacknowledged CSR Reads

Nonacknowledged CSR read commands (NXM) are in a special class of er-
rors. NXMs are used by the console and the operating system to size the
TLSB. In such applications, it is important that the nonacknowledged
read error be reported to the DECchip 21164 synchronous to the issuance
of the offending DECchip 21164 Read_Block command and in an un-
masked fashion. Further, it is important that the NXM not result in a
fault that would cause much of the system to reset.
When a CPU module detects a nonacknowledged CSR read, it reports the
error to the DECchip 21164 through the FILL_ERROR signal. Specifi-
cally, the CPU lets the DECchip 21164 finish the fill cycle, but asserts
FILL_ERROR. This causes the DECchip 21164 to vector to the SCB sys-
tem machine check entry point (offset 660 hex), regardless of the DECchip
21164's current IPL.

3.5.2 Address Bus Errors

The following errors detected by the CPU module are related to the ad-
dress bus:
3-16 CPU Module
• Data Timeout Error (DTO)
• Data Status Error (DSE)
• Sequence Error (SEQE)
• Data Control Transmit Check Error (DCTCE)
• Address Bus Transmit Check Error (ABTCE)
• Unexpected Acknowledge Error (UACKE)
• Memory Mapping Register Error (MMRE)
• Bank Busy Error (BBE)
• Request Transmit Check Error (RTCE)
• Fatal No Acknowledge Error (FNAE)
• Address Bus Parity Error (APE)
• Address Transmit Check Error (ATCE)
• Fatal Data Transmit Check Error (FDTCE)
• Acknowledge Transmit Check Error (ACKTCE)
• DECchip 21164 to MMG Address Parity Error (E2MAPE)
• MMG to ADG Address Parity Error (M2AAPE)
• Transmit check errors
• Command field parity errors
• No acknowledge errors
• Unexpected Acknowledge Error (UACKE)
• Memory Mapping Register Error (MMRE)