Chapter 1: Hardware Description

On the 4538 board, the serial EEPROM content disables the windows. By default, no Local to PCI window is enabled. It is not recommended using these windows for transfers from or to the PCI local space, because this mechanism can result in bad performance, depending on the other PCI devices tied to the PCI bus.

The local base address of each window is defined in PowerSpan internal register

PB_SIx_BADDR. Note that the window must be mapped in the local space between 0xC0000 0000 and 0xCFFF FFFF, in order to comply with the card local space usage. Each window can be moved on the PCI memory or I/O space, using a PowerSpan translation register (PB_SIx_TADDR), so that even a small window can allow access to any part of the PCI space.

During a PowerQUICC II access to the PCI space, the high-order address bits on the PCI bus are generated by the PowerSpan (as defined in the PowerSpan PB_SIx_BADDR register) and the low-order address bits on the PCI bus come from the local address. This mode is called “Address Translation” in the PowerSpan Manual.

NOTE

APowerSpan Local-to-PCI window must be enabled in the PB_SIx_CTL register. Bits IMG_EN (“Image Enable”) and TA_EN (“address translation enable”) must be set.

Figure 1-5 on page 26 illustrates the Local-to-PCI window mechanism:

4538 Hardware Reference Manual

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