Chapter 7. PCI Bus Interface
7-27
PCI Bus Transactions
7.4.5.2.2 Type 1 Configuration Translation
For type 1 translations, the MPC8240 copies the 30 high-order bits of the CONFIG_ADDR
register (without modification) onto the AD[31:2] signals during the address phase. The
MPC8240 automatically translates AD[1:0] into 0b01 during the address phase to indicate
a type 1 configuration cycle.
7.4.6 Other Bus Transactions
There are two other PCI transactions that the MPC8240 supports—interrupt-acknowledge
and special cycles. As an initiator, the MPC8240 may initiate both interrupt-acknowledge
and special-cycle transactions; however, as a target, the MPC8240 ignores
interrupt-acknowledge and special-cycle transactions. Both transactions make use of the
CONFIG_ADDR and CONFIG_DATA registers described in Section 7.4.5.2, “Accessing
the PCI Configuration Space.”
7.4.6.1 Interrupt-Acknowledge Transactions
The PCI bus supports an interrupt-acknowledge transaction. The interrupt-acknowledge
command is a read operation implicitly addressed to the system interrupt controller. Note
that the PCI interrupt-acknowledge command does not address the MPC8240’s EPIC
processor interrupt-acknowledge register and does not return the interrupt vector address
from the EPIC unit. See Chapter 11, “Embedded Programmable Interrupt Controller
(EPIC) Unit,” for more information about the EPIC unit.
When the MPC8240 detects a read 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, the bus
number corresponds to the local PCI bus (bus number = 0x00), the device number is all 1s
(0b1_1111), the function number is all 1s (0b111), and the register number is zero
(0b00_0000), then the MPC8240 performs an interrupt-acknowledge transaction. If the bus
number indicates a nonlocal PCI bus, the MPC8240 performs a type 1 configuration cycle
translation, similar to any other configuration cycle for which the bus number does not
match.
The address phase contains no valid information other than the interrupt-acknowledge
command (C/BE[3:0] = 0b0000). Although there is no explicit address, AD[31:0] are
driven to a stable state, and parity is generated. Only one device (the system interrupt
controller) on the PCI bus should respond to the interrupt-acknowledge command by
asserting DEVSEL. All other devices on the bus should ignore the interrupt-acknowledge
command. As stated previously, the MPC8240’s EPIC unit does not respond to PCI
interrupt-acknowledge commands.
During the data phase, the responding device returns the interrupt vector on AD[31:0] when
TRDY is asserted. The size of the interrupt vector returned is indicated by the value driven
on the C/BE[3:0] signals.
Summary of Contents for MPC8240
Page 1: ...MPC8240UM D Rev 1 1 2001 MPC8240 Integrated Processor User s Manual ...
Page 38: ...xviii MPC8240 Integrated Processor User s Manual TABLES Table Number Title Page Number ...
Page 48: ...xlviii MPC8240 Integrated Processor User s Manual Acronyms and Abbreviations ...
Page 312: ...6 94 MPC8240 Integrated Processor User s Manual ROM Flash Interface Operation ...
Page 348: ...7 36 MPC8240 Integrated Processor User s Manual PCI Host and Agent Modes ...
Page 372: ...8 24 MPC8240 Integrated Processor User s Manual DMA Register Descriptions ...
Page 394: ...9 22 MPC8240 Integrated Processor User s Manual I2O Interface ...
Page 412: ...10 18 MPC8240 Integrated Processor User s Manual Programming Guidelines ...
Page 454: ...12 14 MPC8240 Integrated Processor User s Manual Internal Arbitration ...
Page 466: ...13 12 MPC8240 Integrated Processor User s Manual Exception Latencies ...
Page 516: ...16 14 Watchpoint Trigger Applications ...
Page 538: ...B 16 MPC8240 Integrated Processor User s Manual Setting the Endian Mode of Operation ...
Page 546: ...C 8 MPC8240 Integrated Processor User s Manual ...
Page 640: ...INDEX Index 16 MPC8240 Integrated Processor User s Manual ...