Although these first devices are limited to a maximum of 16 kilobytes of memory, they also pack quite a variety of useful analog and digital peripherals. These include: a 10-bit analog to digital converter, a low power analog comparator with the ability to generate an external voltage reference, up to three serial interfaces depending on which protocol is used, 5 general purpose 16-bit timers, a real time clock with calendar and alarm function, a 32-bit multiplier, direct memory access for low power peripheral operation, and up to 33 IO pins that are all capable of generating an interrupt. The MSP430 FR57xx devices come in packages from a 4x4 mm 24 pin or 7x7 mm 40 pin QFN or a 28 or 38 pin TSSOP. All devices are fully qualified from -40 to 85°C. All devices also include a small amount of RAM for ease of porting applications, storing highly used variables, and containing the 2 way 4 word cache. This will be discussed further in a bit.