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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

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

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

1 2 ... 223 224 225 226 227 228 229 230 231 232 233 ... 359 360

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