Motorola MVME197LE user manual Flash Memory, Onboard Dram, Battery Backup RAM and Clock

Functional Description

BOOT ROM

Currently a socket (socket will be removed from module in later board revisions) for a 32-pin PLCC/CLCC ROM/EPROM referred to as BOOT ROM or DROM (Download ROM) is provided. It is organized as a 128K x 8 device, but as viewed from the processor it looks like a 16K x 64 memory. This memory is mapped starting at location $FFF80000, but after a local reset it is

4also mapped at location 0, providing a reset vector and bootstrap code for the processor. The DR0 bit in the General Control Register (GCR) of the PCCchip2 must be cleared to disable the BOOT ROM memory map at 0.

FLASH Memory

Up to 1MB of FLASH memory is available on the board. FLASH memory works like EPROM, but can be erased and reprogrammed by software. It is organized as 32 bits wide, but to the processor it looks as 64 bits wide. It is mapped at location $FF800000. Reads can be of any size, including burst transfers, but writes are always 32 bits wide, regardless of the size specified for the transfer. For this reason, software should only use 32-bit write transfers. This memory is controlled by the BusSwitch, and the memory size, access time, and write enable capability can be programmed via the ROM Control Register (ROMCR) in the BusSwitch. The FLASH memory can be accessed from the processor bus only. It is not accessible from the local peripheral bus or VMEbus.

Onboard DRAM

The MVME197LE onboard DRAM (2 banks of 32MB memory, one optionally installed) is sized at 32MB using 1M x 4 devices and configured as 256 bits wide. The DRAM is four-way interleaved to efficiently support cache burst cycles. The DRAM is controlled by the DCAM and ECDM, and the map decoders in the DCAM can be programmed through the I2Cbus interface in the ECDM to accommodate different base address(es) and sizes. The onboard DRAM is not reset by a local peripheral bus reset. Refer to the DCAM and ECDM chapters in the MVME197LE, MVME197DP, and MVME197SP Single Board Computers Programmer’s Reference Guide for detailed programming information.

Battery Backup RAM and Clock

The MK48T08 RAM and clock chip is used on the MVME197LE. This chip provides a time of day clock, oscillator, crystal, power fail detection, memory write protection, 8KB of RAM, and a battery in one 28-pin package. The clock provides seconds, minutes, hours, day, date, month, and year in BCD 24-hour

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