
Register Descriptions
Register Map
150
EPC User
’
s Manual Revision 1.05
Copyright 1997-2000, V3 Semiconductor Inc.
LB_MAP0, 1: LOCAL BUS TO PCI BUS ADDRESS MAP 0, 1
Mnemonic:
Offset:
Size:
LB_MAP0,1
5EH, 62H
16 bits
LB_MAP0, 1
Bits
Mnemonic
Type
Reset
Value
Description
15-4
MAP_ADR
FRW
0H
Map Address: These bits correspond to bits AD[31:20] in PCI
address space when a Local to PCI access is made. Address
bits AD[19:2] are derived from the local bus itself. If the size of
the aperture is increased, then the lower bits of MAP_ADR
become masked off according to the ADR_SIZE bits in the
LB_BASE registers.
Access Type: Determines which PCI bus command will be driven
for local bus to PCI bus access:
a
000 = Interrupt Acknowledge (Read)
001 = I/O Read/Write
011 = Memory Read/Write
101 = Configuration Read/Write
110 = Memory Read Multiple/Memory Write
others = reserved
Low Address Override Enable: When Set (1) the AD[1:0] value
transmitted during the address phase will be generated from the
AD_LOW value in the PCI_CFG register. When cleared (0) the
value of AD[1:0] will be
“
00
”
except for I/O cycles where AD[1:0]
correspond to the byte enables.
3-1
TYPE
FRW
0H
a. The value in this bit field is driven on the C/BE[3:1] PCI bus pins directly (except for TYPE="110":
see note). C/BE0 is set based on whether the cycle is a read (0) or a write (1). No checking is done
by the EPC device to see if the command type is supported (see the "Aperture Operation" section
for more details). Reserved combinations can be used to generate other PCI commands directly.
0
AD_LOW_EN
FRW
0H