The RCM5600W/RCM6600W modules do not include a battery, but there is provision for customer-supplied battery backup. Battery backup keeps the Rabbit 5000/6000 real-time clock running while also preserving content of the RCM5600W/RCM6600W families’ battery-backable 32 KB SRAM as well as the RCM6650W module’s external SRAM. Note that for the RCM5600W family, Dynamic C supports battery backup for only a 32 KB portion of the external SRAM