CPC700 User’s Manual—Preliminary
5-25
Since the reset value of the PTM 2 Enable bit is undefined, users who do not use PTM 2 should ensure it
is disabled properly during PCI initialization. To properly disable PTM 2 first set the Enable bit (allowing
write access to PTM BAR 2), set PTM 2 BAR to zero, then clear the Enable bit.
5.9.1.16 PTM 2 Local Address
PLB Address:
FF40_003Ch
Width:
32 bits
Reset Value:
Undefined
Access:
Read/Write
This register defines the local (PLB) address that is generated in response to a PCI access to local (PLB)
space through PTM 2. See PTM 1 Local Address for details.
5.9.2 PCI Configuration Register and Cycles
The processor can generate Configuration cycles on the PCI bus and access the CPC700 PCI configura-
tion registers using the PCICFGADR and PCICFGDATA registers that are found in PLB address space.
PCICFGADR and PCICFGDATA are implemented as specified in PCI Local Bus Specification v2.1, Sec-
tion 3.7.4 (Configuration Mechanism #1), except that they are located at addresses FEC0_0000 and
FEC0_0004 instead of CF8h and CFCh, and are named PCICFGADR and PCICFGDATA instead of
CONFIG_ADDRESS and CONFIG_DATA.
PCICFGADR and PCICFGDATA should be accessed with single beat PLB transactions.
5.9.2.1 Configuration Mechanism
The general mechanism for accessing PCI configuration space is to write a value into PCICFGADR which
specifies the PCI bus, the device on that bus, and the configuration register in that device being accessed.
Then, if the enable bit in PCICFGADR is set, a read or write to PCICFGDATA will cause the bridge to trans-
late the PCICFGADR value into a configuration cycle on the PCI bus.
Table 49.PTM 2 Size/Attribute Register Bits
Bit(s)
Name
Description
0
Enable
This bit determines if range 2 is enabled to map PCI Memory space to
PLB space.
Set PTM 2 BAR to zero before disabling this bit.
When disabled, PTM 2 BAR cannot be written, and reading PTM 2 BAR
will return zeroes.
11:1
Reserved
Returns zero when read.
31:12
Size
The Size defines the size of the region of PCI Memory space that is
mapped to local (PLB) space through PTM 2. For example, a value of
FF00_0000h indicates that the region is 16M bytes in size. The minimum
range size is 4k bytes.
Содержание CPC700
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