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I2O Interface
Enabling I2O Operation
Copyright 1997-2000, V3 Semiconductor Inc.
EPC User
’
s Manual Revision 1.05
109
whenever the outbound post list is not empty. The status register is mapped into offset 0x30
in the ATU PCI address space (as determined by PCI_I2O_BASE) and the mask register
adjacent to it at offset 0x34. These are 32 bit registers when accessed from the I2O ATU
with only a single bit defined in the lowest byte. The same register can also be accessed
from the standard PCI and local bus internal register apertures in the same manner as any
other internal register. However, the registers are defined as 8 bit in these cases.
12.4.1
I
2
O Ready Interrupt
The I2O specification requires that if interrupts are to be used then an interrupt mask and
status register are to be provided at offsets 0x34 and 0x30 in the base address region
allocated to BAR0 (configuration space offset 0x10: PCI_I2O_BASE). These registers are
provided by aliasing the OUT_POST bits of
12.5
ENABLING I
2
O OPERATION
The EPC is configured for I
2
O operation by setting the I2O_EN bit in the PCI_CFG register.
When configured for I
2
O operation, some of the EPC internal operations change:
PCI_IO_BASE register is re-located to offset 0x18 (0x10 is the default)
PCI_BASE1 and PCI_MAP1 are disabled
PCI_I2O_BASE is enabled at offset 0x10 in the EPC internal register space.
PCI_I2O_IMASK (offset 0x34)
Type
Reset
R
0H
reserved
Outbound Post Mask: when clear (0) the interrupt pin 0 is driven
whenever the outbound post FIFO is not empty. Setting this mask
bit disables the physical interrupt pin from being driven but has no
effect on the corresponding status bit in PCI_I2O_ISTAT. This bit
is aliased to the OUT_POST bit in PCI_INT_CFG except in the
opposite polarity (
’
1
’
= enabled in PCI_INT_CFG whereas
’
0
’
=
enabled in PCI_I2O_MASK). Changes to PCI_I2O_MASK bit 3
will also be reflected in PCI_INT_CFG.
R
0H
reserved
Bits
31-4
Mnemonic
-
Description
3
OUT_POST
FRW
0H
2-0
-
PCI_I2O_ISTAT (offset 0x30)
Reset
0H
reserved
Outbound Post Status: set (1) whenever the outbound post FIFO
is not empty. Cleared when the outbound post FIFO is empty
again. The state of the corresponding mask bit has no effect on
this status bit. This bit is aliased to the OUT_POST bit in
PCI_INT_STAT.
0H
reserved
Bits
31-4
Mnemonic
-
Type
R
Description
3
OUT_POST
FRW
0H
2-0
-
R