The TPMC917 is a standard single-width 32bit PMC
module providing 4MByte of SRAM with battery backup by
an on board lithium cell and four ESD protected RS232
channels (TPMC917-10R only).
The 4MByte of NV-SRAM are organized in two banks,
each providing 512K x 32bit of memory. During normal
operation (standard 5V supply applied to the SRAM) the
capacity of the lithium cell is monitored every 24 hours by
a battery monitor device and an interrupt can be
generated if the battery voltage is too low.
The monitor device switches the power supply of the
SRAM from the standard 5V to the battery if the 5V supply
drops below the battery monitor device threshold level.
Any active access to the SRAM at this point is executed
correctly within 1.5µs. After this time any further accesses
to the SRAM are not possible.
A miniature DIP switch allows the selection of the battery
backup source either from the on board lithium cell or from
an external battery via the P14 I/O connector.