Motorola IH5, MCPN750A manual CompactPCI Bus Interface

Block Diagram

CompactPCI Bus Interface

The CompactPCI bus interface is provided using the Intel 21554 non- transparent PCI-to-PCI bridge chip. This device implements a 64-bit primary data bus and 64-bit secondary data bus interface and is PCI 2.1 compliant. The 21554 provides read/write data buffering in both directions.

Unlike a transparent PCI-to-PCI bridge, such as the 21154, the 21554 is designed to bridge two processor domains. The system CompactPCI bus is connected to the primary bus side of the bridge, which is also referred to as the host domain or the host processor side. The secondary bus interfaces to the MCPN750A board local PCI bus, referred to as the local domain or local processor side. The 21554 supports independent primary and secondary address spaces and address translation between the two processor domains. The 21554 accepts a Type 0 configuration header and the configuration space is accessible from both primary and secondary buses. Refer to the MCPN750A CompactPCI Single Board Computer Programmers Reference Guide (MCPN750A/PG) for additional information and programming details.

The 21554 also provides for independent primary and secondary PCI clocks which means that the MCPN750A SBC has it’s own local processor/PCI bus clock source independent of the system backplane clocks.

The 21554 has an I2O message unit which enables the local processor to function as an intelligent I/O processor in an I2O capable system. The device also has an interrupt output for each of the primary and secondary PCI buses. These interrupts may be asserted by the I2O messaging unit or by software writes to an interrupt request register.

The 21554 supports +3.3V or +5V signalling at the PCI buses with a separate VIO pin for the primary and secondary bus I/O’s. The secondary bus signalling voltage is tied to +5V for compatibility with +5V PMCs. The primary bus signalling voltage is tied to the CPCI bus VIO, so the MCPN750A is a universal board that may operate in a +3.3V or +5V chassis.

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