Freescale 68HC12
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The 68HC12 (6812 or HC12 for short) is a 16-bit microcontroller family from Freescale Semiconductor. Originally introduced in the mid 1990s, the architecture is an enhancement of the Freescale 68HC11. Programs written for the HC11 are usually compatible with the HC12, which has a few extra instructions. The first 68HC12 derivatives had a maximum bus speed of 8MHz and flash memory sizes up to 128 kB.
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[edit] Architecture of the 68HC12
Like the 68HC11, the 68HC12 has 2 8-bit accumulators A and B (referred to as a single 16-bit accumulator, D, when A & B are cascaded so as to allow for operations involving 16 bits), 2 16-bit registers X and Y, a 16-bit program counter, a 16-bit stack pointer and an 8 bit Condition Code Register.
[edit] HCS12/MC9S12 derivatives
Beginning in 2000 the family was extended with the introduction of the MC9S12 derivatives which have bus speeds of up to 25 MHz and flash sizes up to 512 kB.
The MC9S12NE64 was introduced by Freescale in September 2004, claiming to be the "industry's first single-chip fast-Ethernet Flash microcontroller." It features a 25 MHz HCS12 CPU, 64 kB of FLASH EEPROM, 8 kB of RAM, and an Ethernet 10/100 Mbit/s controller.
[edit] MC9S12X derivatives
The MC9S12XDP512 which was introduced in 2004 has a bus speed of 40 MHz and a peripheral co-processor known as the XGATE which allows for some tasks to be offloaded from the CPU. The CPU of the S12X derivative also features several new instructions to increase performance.
Freescale announced the MC9S12XEP100 in May 2006 to further extend the S12X family to 50MHz bus speed and add a Memory protection unit (based on segmentation) and a hardware scheme to provide Emulated EEPROM.
[edit] External links
- Free real-time kernel source code for HCS12 with sample apps
- Freescale's official OpenTCP project on SourceForge for MC9S12NE family
- http://hc12text.com/
- http://ee.cleversoul.com/hc12.html
- http://hc12web.de/
- MiniIDE development environment that works with both 68HC11 and 68HC12
- Open source editor with syntax highlighting for the HCS12(X)
- Download open source assembler for HCS12, HCS12X and XGATE written in Perl
- 68HC12 Discussion Group
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