Emerson PMPPC7448 On-CardMemory Configuration:On-CardSDRAM, On-Cardsdram, Nvram Allocation

On-Card Memory Configuration:On-Card SDRAM

Caution:

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If booting from user Flash, the MV64460 controller initially maps one megabyte addressing of Flash memory (beginning at FF80,000016) at the top of the address space. When an 8-bit Flash device is installed in the PLCC socket, it always appears at F800,000016 (and is mir- rored at FF80,000016 when the socket is the boot device).

When removing socketed PLCC devices, always use an extraction tool designed specifically for that task. Otherwise, you risk damaging the PLCC device.

Since the 16-bit Flash device is soldered, an 8-bit ROM could be used to bootstrap the pro- cessor and execute a routine that programs the soldered Flash from a serial port, Ethernet, or through the PCI interface.

ON-CARD SDRAM

The PmPPC7448 supports 256 megabyte, 512 megabyte, 1 gigabyte, and 2 gigabyte con- figurations of 72-bit wide SDRAM. This interface implements eight additional bits to permit the use of error-correcting code (ECC).

A low profile, small-outline, dual inline memory module (SO-DIMM) is installed to reduce board density and routing constraints. A serial EEPROM on the module provides the serial presence detects (SPD). On-card SDRAM occupies physical addresses from 0000,000016 to 7FFF,FFFF16. The SDRAM is controlled by the MV64460 DRAM controller, which may be pro- grammed for most memory sizes and speeds, various block sizes, and write protection.

In addition to the basic SDRAM control functions, the MV64460 chip provides several addi- tional DRAM-related functions and contains the following performance enhancing fea- tures:

•Supports page mode—minimizing SDRAM cycles on multiple transactions to the same SDRAM page and can be configured to support up to 16 simultaneously opened pages.

•Supports error-correcting code (ECC) and read-modify-write (RMW) in the case of partial writes (smaller than 64-bit) to DRAM.

•ECC provides single bit correction and two bits detection.

NVRAM ALLOCATION

The PmPPC7448 uses an eight kilobyte SROM attached to the MV64460 bridge for storing non-volatile information such as board, monitor, and operating system configurations, as well as information specific to user application. All Emerson-specific data is stored in the upper two kilobytes of the device. The remainder of the device is available for user applica- tion. Table 4-3defines the organization of data within the SROM.

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PmPPC7448 User’s Manual 10006757-02