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PCI Bus Controller
22-32
Freescale Semiconductor
Though this device supports many PCI commands as an initiator, the communication subsystem initiator
interface should use PCI
MEMORY
READ
and
MEMORY
WRITE
commands.
22.4.1.5
Addressing
PCI defines three physical address spaces: PCI memory space, PCI I/O space, and PCI configuration
space. Every device for every PCI transaction performs address decoding on the PCI bus. Each agent is
responsible for decoding its own address. The PCI specification supports two types of address decoding:
positive decoding and subtractive decoding (refer to
Section 22.4.1.5.4, “Address Decoding”
). The
address space accessed depends primarily on the type of PCI command used.
22.4.1.5.1
Memory Space Addressing
For memory accesses, PCI defines two types of burst ordering controlled by the two low-order bits of the
address: linear incrementing (AD[1:0] equals 0b00) and cache wrap mode (AD[1:0] equals 0b10). The
other two AD[1:0] encodings (0b01 and 0b11) are reserved.
For linear incrementing mode, the memory address is encoded/decoded using PCI_AD[31:2]. Thereafter,
the address increments by 4 bytes after each data phase completes until the transaction terminates or
completes (a 4 byte data width per data phase is implied). The two low-order bits of the address are still
included in all the parity calculations.
As an initiator, the PCI controller supports linear incrementing and cache wrap mode. When an internal
bus burst transaction is wrapped for memory transactions, the cache wrap mode automatically generates.
For zero-word-aligned bursts and single-beat transactions, the PCI controller drives AD[1:0] to 0b00.
As a target, PCI controller treats cache wrap mode as a reserved memory mode when the cache line size
field is cleared, PCICR1[CLS]. The PCI controller returns the first beat of data and signals a disconnect
without data on the second data phase. When the cache line size field is programmed to a non-zero value,
cache wrap bursts break up and transfer linearly on the internal bus. Reads from the PCI controller,
implemented as delayed reads, always disconnect at the cache line boundary. The PCI controller is not
optimized for wrapping bursts.
1110
MEMORY
READ
LINE
Yes
Yes
The
MEMORY
READ
LINE
command indicates an initiator
requests the transfer of an entire cache line. For the PCI
controller, the
MEMORY
READ
LINE
functions the same as the
MEMORY
READ
command. Cache line wrap is not
implemented.
1111
MEMORY
WRITE
AND
INVALIDATE
Yes (DMA
access only)
Yes
The
MEMORY
WRITE
AND
INVALIDATE
command indicates an
initiator transfers an entire cache line; if this data is in any
cacheable memory, that cache line needs to be invalidated.
The
MEMORY
WRITE
AND
INVALIDATE
functions the same as
the
MEMORY
WRITE
command. Cache line wrap is not
implemented.
Table 22-26. PCI Bus Commands (continued)
PCI_CBE[3:0]
PCI Bus
Command
PCI Controller
Supports as
Initiator
PCI Controller
Supports as
Target
Definition
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 ...