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PCI Bus Controller
Freescale Semiconductor
22-41
22.4.3.4
Special Cycle Transactions
When the PCI controller detects a write to an I/O defined window (
Section 22.3.2.6, “Initiator Window
Configuration Register (PCIIWCR)”
), it checks the enable flag, bus number, and the device number in the
PCICAR register (
Section 22.3.2.12, “Configuration Address Register (PCICAR)”
). If the PCICAR[E] bit
is set, the bus number corresponds to the local PCI bus (bus number equals 0x00), the device number is all
1s (device number equals 0b1_1111), a
SPECIAL
CYCLE
transaction initiates. If the bus number indicates a
subordinate PCI bus (bus number ! equals 0x00), a Type 1 configuration cycle is initiated, similar to any
other configuration cycle the bus number does not match. The function number and Dword values are
ignored.
The
SPECIAL
CYCLE
command (0b0001) is driven on the PCI_CBE[3:0] signals and the address bus is
driven with a stable pattern during the address phase, but contains no valid address information. The
SPECIAL
CYCLE
command contains no explicit destination address, but broadcasts to all agents on the same
bus segment. Each receiving agent must determine whether the message is applicable to it. PCI agent never
asserts PCI_DEVSEL in response to a
SPECIAL
CYCLE
command. Master abort is the normal termination
for a
SPECIAL
CYCLE
and no errors report for this case of master abort termination. This command is
basically a broadcast to all agents, and interested agents accept the command to process the request.
NOTE
SPECIAL
CYCLE
commands do not cross PCI-to-PCI bridges. If a master
wants to generate a
SPECIAL
CYCLE
command on a specific bus in the
hierarchy not its local bus, it must use a Type 1
CONFIGURATION
WRITE
command to do so. Type 1
CONFIGURATION
WRITE
commands can traverse
PCI-to-PCI bridges in both directions for the purpose of generating
SPECIAL
CYCLE
commands on any bus in the hierarchy and are restricted to a single
data phase in length. However, the master must know the specific bus it
desires to generate the
SPECIAL
CYCLE
command on and cannot simply do a
broadcast to one bus to expect it to propagate to all buses.
During the data phase, PCI_AD[31:0] contains the
SPECIAL
CYCLE
message and an optional data field. The
SPECIAL
CYCLE
message encodes on the 16 least significant bits (PCI_AD[15:0]) and the optional data
field encodes on the most significant bits (PCI_AD[31:16]). The PCI SIG steering committee assign the
SPECIAL
CYCLE
message encodings.
provides the current list of defined encodings.
Table 22-30. Special Cycle Message Encodings
PCI_AD[15:0]
Message
0x0000
SHUTDOWN
0x0001
HALT
0x0002
x86 architecture-specific
0x0003 – 0xFFFF
—
Summary of Contents for MCF54455
Page 33: ...xxviii Freescale Semiconductor ...
Page 67: ...Freescale Semiconductor 1 ...
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 ...
Page 842: ...I2 C Interface Freescale Semiconductor 33 16 ...
Page 843: ...Freescale Semiconductor 1 ...
Page 921: ...Revision History A 6 Freescale Semiconductor ...