Chapter 4. Configuration Registers
4-11
PCI Interface Configuration Registers
System software may need to scan the PCI bus to determine what devices are actually
present. To do this, the configuration software must read the vendor id in each possible PCI
slot. If there is no response to a read of an empty slot, the MPC8240 returns 0xFFFF (the
invalid vendor id). Any configuration write cycle to a reserved register is completed
normally and the data is discarded.
Note that the MPC8240 must not issue PCI configuration transactions to itself (that is, for
PCI configuration transactions initiated by the MPC8240, its IDSEL input signal must not
be asserted).
4.2.1 PCI Command Register—Offset 0x04
The following subsections describe the MPC8240 PCI configuration registers in detail.
The 2-byte PCI command register, shown in Figure 4-3, provides control over the ability to
generate and respond to PCI cycles. Table 4-5 describes the bits of the PCI command
register.
Figure 4-3. PCI Command Register—0x04
0x30
Expansion ROM base
address
This register is read-only. The default value has 0b0 in bit 0, defining the
expansion ROM base address register as disabled in the MPC8240.
0x34–0x3B
—
Reserved for future use by PCI
0x3C
Interrupt line
Contains interrupt line routing information
0x3D
Interrupt pin
Indicates which interrupt pin the device (or function) uses
(0x00 = no interrupt pin)
0x3E
MIN GNT
Specifies the length of the device’s burst period
(0x00 indicates that the MPC8240 has no major requirements for the
settings of latency timers.)
0x3F
MAX LAT
Specifies how often the device needs to gain access to the PCI bus
(0x00 indicates that the MPC8240 has no major requirements for the
settings of latency timers)
0x43
—
Reserved on the MPC8240
Table 4-4. PCI Configuration Space Header Summary (Continued)
Address
Offset
Register Name
Description
Reserved
0 0 0 0_0 0
0
0
15
10
9
8
7
6
5
4
3
2
1
0
Fast back-to-back
SERR
Parity error response
Memory-write-and-invalidate
Special cycles
Bus master
Memory space
I/O space
Summary of Contents for MPC8240
Page 1: ...MPC8240UM D Rev 1 1 2001 MPC8240 Integrated Processor User s Manual ...
Page 38: ...xviii MPC8240 Integrated Processor User s Manual TABLES Table Number Title Page Number ...
Page 48: ...xlviii MPC8240 Integrated Processor User s Manual Acronyms and Abbreviations ...
Page 312: ...6 94 MPC8240 Integrated Processor User s Manual ROM Flash Interface Operation ...
Page 348: ...7 36 MPC8240 Integrated Processor User s Manual PCI Host and Agent Modes ...
Page 372: ...8 24 MPC8240 Integrated Processor User s Manual DMA Register Descriptions ...
Page 394: ...9 22 MPC8240 Integrated Processor User s Manual I2O Interface ...
Page 412: ...10 18 MPC8240 Integrated Processor User s Manual Programming Guidelines ...
Page 454: ...12 14 MPC8240 Integrated Processor User s Manual Internal Arbitration ...
Page 466: ...13 12 MPC8240 Integrated Processor User s Manual Exception Latencies ...
Page 516: ...16 14 Watchpoint Trigger Applications ...
Page 538: ...B 16 MPC8240 Integrated Processor User s Manual Setting the Endian Mode of Operation ...
Page 546: ...C 8 MPC8240 Integrated Processor User s Manual ...
Page 640: ...INDEX Index 16 MPC8240 Integrated Processor User s Manual ...