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21555 Non-Transparent PCI-to-PCI Bridge User Manual 109
Error Handling
Data Parity
Error on
Secondary
Bus
Downstream
Posted Write
— | 0 Transaction completes normally on secondary bus.
— | 1
• Transaction completes on secondary bus.
• Sets secondary Data Parity Detected bit when s_perr_l is asserted.
1 | 1
• Transaction completes on secondary bus.
• Sets secondary Data Parity Detected bit when s_perr_l is asserted.
• Asserts p_serr_l when no parity error detected on primary bus.
Upstream
Posted Write
— | 0
• Forwards transaction with parity error.
• Sets secondary Detected Parity Error bit.
— | 1
• Forwards transaction with parity error.
• Sets secondary Detected Parity Error bit.
• Asserts s_perr_l.
Downstream
Delayed
Write
— | 0 Transaction completes normally on secondary bus.
— | 1
• Transaction completes normally on secondary bus.
• Sets secondary Data Parity Detected bit when s_perr_l is asserted.
1 | 1
• Transaction completes normally on secondary bus.
• Sets secondary Data Parity Detected bit when s_perr_l is asserted.
• Asserts p_perr_l when returning p_trdy_l to initiator on primary
bus (for both CSR and BAR forwarding mechanisms).
Upstream
Delayed
Write
— | 0 Transaction completes normally on secondary bus.
— | 1
• Returns TRDY# (and STOP# if multiple data phases requested).
• Transaction not forwarded.
• Sets secondary Parity Error Detected bit.
• Asserts s_perr_l.
Downstream
Delayed
Read
— | 0
• Returns read data with bad parity to initiator (for both CSR and BAR
forwarding mechanisms).
• Sets secondary Parity Error Detected bit.
— | 1
• Returns read data with bad parity to initiator (for both CSR and BAR
forwarding mechanisms).
• Sets secondary Parity Error Detected bit.
• Sets secondary Data Parity Detected bit.
• Asserts s_perr_l.
Upstream
Delayed
Read
— |
—
The 21555 is returning data, all action is taken by initiator.
Configuration
Register or
CSR Write
— | 0
• Writes the data normally.
• Sets the secondary Parity Error Detected bit.
— | 1
• Writes the data normally.
• Sets the secondary Parity Error Detected bit.
• Asserts s_perr_l.
Configuration
Register or
CSR Read
— |
—
Returns read data normally.
Table 29. Parity Error Responses (Sheet 3 of 3)
Type of
Error
Type of
Transaction
PER
†
P|S
Action Taken
† PER: Parity Error Response bit (Primary | Secondary).