PCI Bus Controller
Freescale Semiconductor
22-33
22.4.1.5.2
I/O Space Addressing
For PCI I/O accesses, all 32 address signals provide an address with granularity of a single byte. After a
target has claimed an I/O access, it must determine if it can complete the entire access as indicated by the
byte enable signals. If all selected bytes are not in the address range of the target, the entire access cannot
complete. In this case, target does not transfer any data and terminates the transaction with a target-abort.
22.4.1.5.3
Configuration Space Addressing and Transactions
PCI supports two types of configuration accesses. Their primary difference is the format of the address on
the PCI_AD[31:0] signals during the address phase. The two low-order bits of the address indicate the
format used for the configuration address phase: type 0 (AD[1:0] equals 0b00) or type 1 (AD[1:0] equals
0b01). Both address formats identify a specific device and a specific configuration register for that device:
•
Type 0 configuration accesses select a device on the local PCI bus. They do not propagate beyond
the local PCI bus and are claimed by a local device or terminated with a master-abort.
•
Type 1 configuration accesses target a device on a subordinate bus through a PCI-to-PCI bridge,
see
. Type 1 accesses are ignored by all targets except PCI-to-PCI bridges that pass
the configuration request to another PCI bus.
When the controller initiates a configuration access on the PCI bus, it places the configuration address
information on the AD bus and the configuration command on the PCI_CBE[3:0] bus. Setting AD[1:0] to
0b00 during the address phase indicates a Type 0 configuration transaction. The bit pattern tells the
community of devices on the PCI bus the bridge that owns the PCI bus has already performed the bus
number comparison and verified the request targets a device on its bus.
shows the contents
of the AD bus during the address phase of the Type 0 configuration access.
Table 22-27. PCI I/O Space Byte Decoding
Access Size
PCI_AD[1:0]
PCI_CBE[3:0]
Data
8-bit
00
xxx
0
AD[7:0]
01
xx
01
AD[15:8]
10
x
011
AD[23:16]
11
0111
AD[31:24]
16-bit
00
xxx
0
AD[15:0]
01
xx
01
AD[23:8]
10
x
011
AD[31:16]
24-bit
00
xxx
0
AD[23:0]
01
xx
01
AD[31:8]
32-bit
00
xxx
0
AD[31:0]
Summary of Contents for MCF54455
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Page 125: ...Freescale Semiconductor 1 ...
Page 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
Page 173: ...Cache 6 28 Freescale Semiconductor ...
Page 179: ...Static RAM SRAM 7 6 Freescale Semiconductor ...
Page 207: ...Power Management 9 16 Freescale Semiconductor ...
Page 323: ...Reset Controller Module 13 8 Freescale Semiconductor ...
Page 389: ...Pin Multiplexing and Control 16 44 Freescale Semiconductor ...
Page 575: ...PCI Bus Controller 22 58 Freescale Semiconductor ...
Page 600: ...Advanced Technology Attachment ATA Freescale Semiconductor 23 25 ...
Page 601: ...Freescale Semiconductor 1 ...
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