Programming 31
Table 3-3 PCI Command Register
PCI Command: Offset $04
Bit
Description
Read
Write
*Value after
PCI Reset
0
I/O Space.
Writing a one (1) allows the device to respond to I/O Space
accesses.
Writing a zero (0) disables the device from responding to I/O
Space accesses.
Yes
Yes
0
1
Memory Space
.
Writing a one (1) allows device to respond to Memory Space
accesses.
Writing a zero (0) disables the device from responding to
Memory Space accesses.
Yes
Yes
0
2
Master Enable.
Writing a one (1) allows the device to behave as a bus master.
Writing a zero (0) disables the device from generating bus
master accesses.
Yes
Yes
0
3
Special Cycle.
Not Supported
Yes
No
0
4
Reserved
N/A
N/A
0
5
VGA Palette Snoop
.
Not Supported
Yes
No
0
6
Parity Error Response.
Writing a zero (0) indicates parity error is ignored and the
operation continues.
Writing a one (1) indicates parity checking is enabled.
Yes
Yes
0
7
Wait Cycle Control.
Controls whether a device does address/data stepping.
A zero (0) indicates the device never does stepping.
A one (1) indicates the device always does stepping.
(NOTE: Hardwired to zero (0).)
Yes
No
0
8
SERR# Enable.
Writing a one (1) enables SERR# driver.
Writing a zero (0) disables SERR# driver.
Yes
Yes
0
9
Reserved
N/A
N/A
0
10
Interrupt Disable:
When set (1), this bit disables the Reflective Memory from
asserting its interrupt pin.
When not set (0), interrupts are generated normally.
Yes
Yes
0
15:11
Reserved
Yes
No
$0
*
NOTE
: This register will be altered by the system BIOS during the system boot process (e.g., $0107).