3-24
MPC106 PCIB/MC User's Manual
MOTOROLA
3.2.3.2 PCI Status Register
The 2-byte PCI status register, shown in Figure 3-9, is used to record status information for
PCI bus-related events. The definition of each bit is given in Table 3-13. Only 2-byte
accesses to address offset 0x06 are allowed.
Reads to this register behave normally. Writes are slightly different in that bits can be
cleared, but not set. A bit is cleared whenever the register is written, and the data in the
corresponding bit location is a 1. For example, to clear bit 14 and not affect any other bits
in the register, write the value 0b0100_0000_0000_0000 to the register.
6
Parity error
response
0
This bit controls whether the MPC106 responds to parity errors.
0
Parity errors are ignored and normal operation continues.
1
Action is taken on a parity error. See Chapter 9, “Error
Handling,” for more information.
5
—
0
This bit is reserved.
4
Memory-write-and-
invalidate
0
This bit is hardwired to 0, indicating that the MPC106, acting as a
master does not generate the memory-write-and-invalidate
command. The MPC106 generates a memory-write command
instead.
3
Special-cycles
0
This bit is hardwired to 0, indicating that the MPC106 (as a target)
ignores all special-cycle commands.
2
Bus master
1
This bit controls whether the MPC106 can act as a master on the
PCI bus. Note that if this bit is cleared, 60x to PCI writes will cause
the data to be lost and 60x to PCI reads will assert TEA (provided
the TEA_EN bit in PICR1 is set).
0
Disables the ability to generate PCI accesses
1
Enables the MPC106 to behave as a PCI bus master
1
Memory space
1
This bit controls whether the MPC106 (as a target) responds to
memory accesses.
0
The MPC106 does not respond to PCI memory space
accesses.
1
The MPC106 responds to PCI memory space accesses.
0
I/O space
0
This bit is hardwired to 0, indicating that the MPC106 (as a target)
does not respond to PCI I/O space accesses.
Table 3-12. Bit Settings for PCI Command Register—0x04 (Continued)
Bit
Name
Reset
Value
Description