Embedded Systems/Freescale Microcontrollers
Freescale Semiconductor (formally Motorola Semiconductor Products Sector) spun-off from Motorola in July 2004. Freescale makes many microcontrollers (MCU's) and also a whole host of other devices such as sensors, DSP's and memory, to name a few.
The Freescale Microcontrollers come in 5 families.
- 6800 descendents: 8 bit or 16 bit
- 68000 descendents: 32 bit
- MCORE: 32 bit
- PowerPC family: 32 bit
- ARM family: 32 bit. We discuss ARM core Freescale microcontrollers in another chapter, Embedded Systems/ARM Microprocessors.
There are many variations on the HC08 CPU core; The 68HC908JL8 is one example. the HC908Jl3 offer 256 bytes of RAM (random access memory) and 4K bytes of Flash ROM (Read only memory). The HC08 cores offer a maximum bus speed of 8 MHz, a 20 MHz crystal may be used as the external clock source(as the oscillator is internally divided by 4 to give 8 MHz bus speed). Typical peripheral components of the microcontroller include:
- Two 16 bit, free running timers.
- SCI (serial communications interface,(RS232))
- 12 channel 8-bit Analogue to digital converters (A/D)
The HC08 microcontrollers are usually supplied in 28 pin or 32 pin DIL packages, but can also be obtained in serface-mount SOIC footprints
Freescale HC05 (Legacy)
Freescale HC11 (Legacy)
Freescale HC12 (Legacy)
32-bit Embedded Processors
The 68k family and the nearly-binary-compatible ColdFire family are 32 bit processors capable of running Linux.
There is a Debian Linux port to 68k processors with a MMU. A Debian Linux port to ColdFire processors with a MMU is "in progress".
There are several ColdFire chips that, as of 2008, are available for under $5 (in qty 1). Those low-cost chips do not include a MMU, and so cannot run a full version of Linux. w:uClinux runs on chips without a MMU, and has been ported to some ColdFire chips  on platforms with at least 1 MB of RAM.
Yes, but does uClinux actually run on a chip that costs less than $5 ?
Most (all?) currently manufactured ColdFire and 68k chips are available only in surface mount packages, not in any DIP package.
- First Generation: G1 (601)
- Second Generation: G2 (603, 603e, 604)
- Third Generation: G3 (750, 750CX, 750CX3, 750FX, 750GX)
- Fourth Generation: G4 (7400,7450)
- w:Freescale 68HC12
- w:Freescale ColdFire
- The 68HC12 discussion forum at EmbeddedRelated is still pretty active, apparently because 68HC12 dev boards (such as those from EVBplus) are typically lower-cost than dev boards with most other microcontrollers.
- EE Compendium: resources for using Freescale's HC12 family
- w:Motorola 68000 family