Altera PCI Compiler - Manual (Page 228)

4–18 User Guide Version 11.1 Altera Corporation
PCI Compiler October 2011
Local Reference Design
The dma_bc_la register location includes the following 3 fields:
■ Local address—starting address at which the transaction begins
reading or writing data during a PCI transaction.
■ Byte count—number of DWORDs transferred during a PCI transaction
■ Transaction control—type of transaction to be initiated
1 The byte count field is only used for memory transactions. For
I/O transactions this value is ignored. Because I/O transactions
are always 1 DWORD long, the data is transferred to the 32-bit I/O
register.
Figure 4–4 shows the mapping of the dma_bc_la fields.
Figure 4–4. dma_bc_la Fields
Table 4–11 shows definition of the transaction control field. Although 8
bits are reserved for the transaction control field, only 4 bits are used:
To initiate PCI transactions with Altera PCI MegaCore as a master, you
must perform a 32-bit single-cycle write transaction to the dma_sa
register followed by a 32-bit single-cycle write transaction to the
dma_bc_la
register. The write to the dma_bc_la register triggers the
master control unit, which requests a master transaction and executes it
as indicated in the transaction control part of the dma_bc_la register.
Table 4–11. Transaction Control Field
Transaction Control (Binary) Initiated Transaction Type
0000 32-Bit Memory Read
0010 64-Bit Memory Read
0100 32-Bit I/O Read
0110 32-Bit I/O Write
1000 32-Bit Memory Write
1010 64-Bit Memory Write
Reserved
31...........28 27...........16 15............8 7...............0
Transaction
Control
Byte Count Local
Address
Bit