Freescale Semiconductor MCF5480 - Manual (Page 547)

Functional Description
MCF548x Reference Manual, Rev. 3
Freescale Semiconductor 19-63
assigned by the PCI SIG Steering Committee. The current list of defined encodings are provided in
Table 19-51 .
19.4.4.5 Transaction Termination
If the PCI cycle Master Aborts, the interface will return 0xFFFF FFFF as read data, but complete without
error. It will issue an interrupt to the internal interrupt controller if enabled.
For abnormal transaction termination during an XL bus-initiated transaction ( retry limit reached or target
abort), an error (TEA on XL bus) is generated. It will issue an interrupt to the MCF548x interrupt controller
if such interrupts are enabled.
Transfers that cross the 32-bit boundary (greater than 4 bytes) to a PCI nonmemory address range result
in a transfer error (TEA on XL bus).. The space is defined as nonmemory if the IO/M# configuration bit
associated with that window is programmed “0”.This type of unsupported transfer does not cause an
interrupt.
19.4.5 XL Bus Target Interface
This section discusses the MCF548x as a PCI target, and as such, the following apply:
• The target interface can issue target abort, target retry, and target disconnect terminations.
• The target interface supports fast back-to-back cycles.
• No support of dual address cycles as a PCI target.
• Target transactions are not snooped by the processor.
• Medium device selection timing only.
• Three 32-byte buffers enhance data throughput.
The XL bus Target Interface provides access for external PCI masters to two windows of MCF548x
address space. Target Base Address Translation Registers 0 and 1 allow the user to map PCI address hits
on MCF548x PCI Base Address Registers to areas in the internal address space. All of these registers must
be enabled for this interface to operate.
Table 19-51. Special Cycle Message Encodings
PCIAD[15:0] Message
0x0000 SHUTDOWN
0x0001 HALT
0x0002 x86 architecture-specific
0x0003–0xFFFF —
Table 19-52. Unsupported XL Bus Transfers
XL Bus Transaction PCI Address Space
Burst (32-byte) Nonmemory
> 4 byte Single Beat Nonmemory
4 byte Single Beat at a[29:31] 001, 010, or 011 Nonmemory
3 byte Single Beat at a[29:31] 010 or 011 Nonmemory
2 byte Single Beat at a[29:31] 011 Nonmemory