
3–32 User Guide Version 11.1 Altera Corporation
PCI Compiler October 2011
Configuration Registers
Command Register
Command is a 16-bit read/write register that provides basic control over
the ability of the PCI function to respond to the PCI bus and/or access it.
Refer to Table 3–16.
Table 3–16. Command Register Format
Data
Bit
Mnemonic Read/Write Definition
0
io_ena
Read/write
I/O access enable. When high,
io_ena lets the function respond to
the PCI bus I/O accesses as a target.
1
mem_ena
Read/write
Memory access enable. When high,
mem_ena lets the function
respond to the PCI bus memory accesses as a target.
2
mstr_ena
Read/write
Master enable. When high,
mstr_ena allows the function to request
mastership of the PCI bus. Bit 2 is hardwired to
1 when PCI master
host bridge options are enabled through the wizard.
3Unused– –
4
mwi_ena
Read/write Memory write and invalidate enable. This bit controls whether the
master may generate a MWI command. Although the function
implements this bit, it is ignored. The local side must ensure that the
mwi_ena output is high before it requests a master transaction using
the MWI command.
5Unused– –
6
perr_ena
Read/write
Parity error enable. When high,
perr_ena enables the function to
report parity errors via the
perrn output.
7Unused– –
8
serr_ena
Read/write
System error enable. When high,
serr_ena allows the function to
report address parity errors via the
serrn output. However, to signal
a system error, the
perr_ena bit must also be high.
9Unused– –
10 int_dis Read/write Interrupt disable. A value of 1 disables the PCI MegaCore function
from asserting
intan on the PCI bus. However, the interrupt is only
disabled after the preexisting interrupt has been serviced.
15..11 Unused – –
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