Broadcom BCM5722 Programmer's Manual page 174

BCM5722
Indirect Memory Access
Memory indirect mode operates in the same fashion to register indirect mode. There is a PCI configuration space register
pair, which is used to access the BCM5722 Ethernet controller memory block. The Memory_Window_Base_Address register
positions a pointer/cursor in the local memory block. Unlike the Register_Base_Address register, the
Memory_Window_Base_Address register may position at any valid offset. Access to ranges 0x00000–0x1FFFF is
allowable. The Memory_Window_Data register is the read/write porthole for host software, using the previously positioned
pointer/cursor. This register pair accesses the BCM5722 Ethernet controller local memory block (see
on page 116).
Note: If Indirect Memory Access is performed using memory write cycles (i.e., by accessing the
Memory_Window_Base_Address and Memory_Window_Data registers through memory mapped by the PCI BAR
register), as opposed to PCI configuration write cycles, the host software must insert a read command to the
Memory_Window_Base_Address register between two consecutive writes to the Memory_Window_Base_Address
and Memory_Window_Data registers.
Page 115 Configuration Space
Bro adco m C orp or atio n
Programmer's Guide
10/15/07
Figure 42
Document 5722-PG101-R