Altera PCI Compiler - Manual (Page 166)

3–92 User Guide Version 11.1 Altera Corporation
PCI Compiler October 2011
Master Mode Operation
The pci_mt64 and pci_mt32 functions can generate transactions as
specified in
Table 3–11 . When the local side requests I/O or configuration
cycles, the function automatically issues a 32-bit single-cycle read/write
transaction.
1 The local-side design may require a long time to transfer data
to/from the function during a burst transaction. The local-side
design must ensure that PCI latency rules are not violated while
the function waits for data. Therefore, the local-side device must
not insert more than eight wait states before asserting lm_rdyn.
PCI Bus Parking
By asserting the gntn signal of a master device that has not requested bus
access, the PCI bus arbiter may park on any master device when the bus
is idle. In accordance with the PCI Local Bus Specification, Revision 3.0, if
the arbiter parks on pci_mt64 or pci_mt32, the function drives the
ad[31..0]
, cben[3..0] and par signals.
If the arbiter has parked the bus on pci_mt64 or pci_mt32 and the local
side requests a transaction, the request bit (i.e., lm_tsr[0]) will not be
asserted on the local side. The local state machine will immediately assert
the grant bit (i.e., lm_tsr[1]).
Design Consideration
The arbiter may remove the gntn signal after the local side has asserted
lm_req64n
or lm_req32n to request the bus, but before the master
function has been able to assert the framen signal to claim the bus. In this
case, the lm_tsr signals will transition from the grant state (i.e.,
lm_tsr[1]
asserted) back to the request state (i.e., lm_tsr[0] asserted)
until the arbiter grants the bus to the requesting function again. In
systems where this situation may occur, the local-side logic should hold
the address and command on the l_adi[31..0] and l_cbeni[3..0]
buses until the address phase bit (i.e., lm_tsr[2]) is asserted to ensure
that the pci_mt64 or pci_mt32 function has assumed mastership of the
bus and that the current address and command have been transferred.