Altera PCI Compiler Manuale Utente Scaricare il pdf (Pagina 133)

Altera Corporation User Guide Version 11.1 3–59

October 2011

Functional Description

Figure 3–12 shows a 32-bit PCI side and 64-bit local side burst memory

read target transaction. (This figure only applies to the pci_mt64 and

pci_t64 functions.)

The events in Figure 3–12 are the same as those shown in Figure 3–8,

except that a 64-bit transfer shown in Figure 3–12 takes one clock cycle on

the local side but requires two clock cycles on the PCI side. The function

automatically inserts local side wait states in clock cycles 7 and 9 to

temporarily suspend the local transfer allowing sufficient time for the

data to be transferred on the PCI side. In Figure 3–12, lt_tsr[7] is not

asserted and lt_tsr[9] is asserted indicating that the transaction is a

32-bit burst. If the local side cannot handle 32-bit burst transactions, it

must disconnect after the first local transfer.

Also, because the address of the transaction is not at a QWORD boundary

(ad[2..0] == B"100"), the first DWORD transferred to the PCI side is

the high DWORD. The first low DWORD is not transferred to the PCI side.

The pci_mt64 and pci_t64 functions deassert l_ldat_ackn and

assert l_hdat_ackn during the first data transfer on the local side to

indicate that only the high DWORD is transferred to the PCI side, as shown

in Figure 3–12 at clock cycle 7.

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Altera PCI Compiler Manuale Utente Pagina 133