Motorola MVME162 manual Memory Options, Dram Options, Sram Options

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Board Level Hardware Description

Memory Options

The following memory options are used on the different versions of MVME162 boards.

DRAM Options

The MVME162 implementation includes a 1 MB, 4 MB, or 8 MB DRAM option. The DRAM architecture is non-interleaved for 1 MB and 8 MB; while the 4 MB architecture is interleaved. Parity protection can be enabled with interrupts or bus exception when a parity error is detected. DRAM performance is specified in the section on the DRAM Memory Controller in the MCchip Programming Model in the MVME162 Embedded Controller Programmer’s Reference Guide.

SRAM Options

The MVME162 implementation includes a 512 KB SRAM option. SRAM architecture is single non-interleaved. SRAM performance is specified in the section on the SRAM Memory Controller in the MCchip Programming Model in the MVME162 Embedded Controller Programmer’s Reference Guide. A battery supplies VCC to the SRAMs when main power is removed. The worst case elapsed time for battery protection is 200 days.

The SRAM arrays are not parity protected.

The MVME162 SRAM battery backup function is provided by a Dallas DS1210S. The DS1210S supports primary and secondary power sources. When the main board power fails, the DS1210S selects the source with the highest voltage. If one source should fail, the DS1210S switches to the redundant source. Each time the board is powered, the DS1210S checks power sources and if the voltage of the backup sources is less than two volts, the second memory cycle is blocked. This allows software to provide an early warning to avoid data loss. Because the DS1210S may block the second access, the software should do at least two accesses before relying on the data.

The MVME162 provides jumpers (on J20) that allow either power source of the DS1210S to be connected to the VMEbus +5 V STDBY pin or to one cell of the onboard battery. For example, the primary system backup source may be a battery connected to the VMEbus +5 V STDBY pin and the secondary source may be the onboard battery. If the system source should fail or the board is removed from the chassis, the onboard battery takes over. Refer to Chapter 2 for the jumper configurations.

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