Pci fast back-to-back, Figure 10-9. pci fast back-to-back, 8 pci fast back-to-back – Rainbow Electronics DS31256 User Manual
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10.1.8 PCI Fast Back-to-Back
Fast back-to-back transactions are two consecutive bus transactions without the usually required idle
cycle (PFRAME and PIRDY deasserted) between them. This can only occur when there is a guarantee
that there is not any contention on the signal lines. The PCI specification allows two types of fast back-
to-back transactions—those that access the same agent (Type 1) and those that do not (Type 2).
shows an example of a fast back-to-back transaction where no idle cycle exists. As a bus
master, the Envoy is not capable of performing a Type 2 access. As a target, it can accept both types of
fast back-to-back transactions.
Figure 10-9. PCI Fast Back-To-Back
1
2
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5
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data #1
Address
CMD
BE #1
PCLK
PFRAME
PAD
PCBE
PIRDY
PTRDY
PDEVSEL
data #2
data #2
BE #2
BE #2
Address
data #1
CMD
BE #1