w83c554f Winbond Electronics Corp America, w83c554f Datasheet - Page 39

• Manufacturer Part Number: w83c554f
• Description: System I/o Controller With Pci Arbiter & Ultradma/33 Ide Controller
• Manufacturer: Winbond Electronics Corp America

W83C554F
System Architecture
3.10
PCI Memory Read
The Memory Read command (C/BE[3:0]# = 6h during the address phase) is only used when operating as a bus master. It
will be used when transferring data to memory and the number of data phases is one half or less of the value programmed to
the Cache Line Size Register, or when reading less than 2 Dwords from memory. If the device needs to read more than 2
Dwords from memory, the Memory Read Line command is used. During the Memory Read cycle, the W83C554F issues a
PCI REQ# for the bus and, when PCI GNT# is asserted, reads one Dword from system memory. The bus is then released.
The data phase in Figure 3-6 takes two clock cycles, as determined by TRDY#. The W83C554F activates all byte enables,
even if some byte lanes do not contain valid data. It internally discards unnecessary bytes.
In slave mode, PCI-to-ISA memory reads are supported.
Figure 3-6. Master Memory Read
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