Type 0 Configuration Translation - Motorola MPC8240 User Manual

When the MPC8240 detects an access to the CONFIG_DATA register, it checks the enable
flag and the device number in the CONFIG_ADDR register. If the enable bit is set, and the
device number is not 0b1_1111, the MPC8240 performs a configuration cycle translation
function and runs a configuration-read or configuration-write transaction on the PCI bus.
The device number 0b1_1111 is used for performing interrupt-acknowledge and special-
cycle transactions. See Section 7.4.6, "Other Bus Transactions," for more information. If
the bus number corresponds to the local PCI bus (bus number = 0x00), the MPC8240
performs a type 0 configuration cycle translation. If the bus number indicates a remote PCI
bus (that is, nonlocal), the MPC8240 performs a type 1 configuration cycle translation.
7.4.5.2.1 Type 0 Configuration Translation
Figure 7-10 shows the type 0 translation function performed on the contents of the
CONFIG_ADDR register to the AD[31:0] signals on the PCI bus during the address phase
of the configuration cycle.
Contents of CONFIG_ADDR Register
E 0000000
31 30
AD[31:0] Signals
During Address Phase
IDSEL–only one signal high
31
For type 0 configuration cycles, the MPC8240 translates the device number field of the
CONFIG_ADDR register into a unique IDSEL signal for up to 21 different devices. Each
device connects its IDSEL input to one of the AD[31:11] signals. For type 0 configuration
cycles, the MPC8240 translates the device number to IDSEL as shown in Table 7-6.
Bus Number
24 23
see Table 7-6
Figure 7-10. Type 0 Configuration Translation
Chapter 7. PCI Bus Interface
Device Number
16 15 11 10
Function/Register Number
11 10
PCI Bus Transactions
Reserved
Function Number
Register Number 00
8 7 2 1 0
00
2 1 0
7-25