Motorola MVME187 manual Optional SRAM Battery Backup

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Board Level Hardware Description

Optional SRAM Battery Backup

SRAM battery backup is optionally available on the MVME187, but only as a factory build and only by special request. (Contact your local Motorola sales office for details). The battery backup function, provided by a Dallas DS1210S nonvolatile controller chip and a RAYOVAC FB1225 battery, supports primary and secondary power sources.

The onboard power source is a RAYOVAC FB1225 battery which has two BR1225-type lithium cells and is socketed for easy removal and replacement. A small capacitor is provided to allow the battery to be quickly replaced without data loss (i.e., the battery must be replaced within 30 seconds).

If your MVME187 is equipped with SRAM battery backup, 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, allowing software to provide an early warning to avoid data loss:

❏If the voltage of the backup sources is less than two volts, the second memory access cycle is blocked.

❏Because the DS1210S may block the second access, the software should do at least two accesses before relying on the data.

With the optional battery backup, the MVME187 provides jumpers

(see Optional SRAM Backup Power Source Select Header J6 on page

3-11) 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.

The power leads from the battery are exposed on the solder side of the board, therefore the board should not be placed on a conductive surface or stored in a conductive bag unless the battery is removed.

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