BSCS

Topics: Central processing unit, Processor register, X86 Pages: 5 (942 words) Published: April 10, 2014
Research on the HCS12 microcontroller
1. Provide a picture of the HCS12 / Dragon board.

2. What microcontroller family does the HCS12 belong to?
The 68HC12 (6812 or HC12 for short) is a 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 extrainstructions. The first 68HC12 derivatives had a maximum bus speed of 8 MHz and flash memory sizes up to 128 kB.

3. What is the development studio or software that allows programmers/engineers to program this MCU? In order to know how to program a microcontroller, we need a device called a burner/programmer. A programmer is a hardware device with dedicated software which reads the content of the hex file stored on the PC or the laptop and transfers it to the microcontroller to be burned. It reads the data of the hex file by connecting itself to the PC via a serial or USB cable and transfers the data to the memory of the microcontroller to be programmed in accordance with the protocols as described by the manufacturer in the datasheet. 4. Provide a screenshot of #3.

5. How many accumulators does it have and what are they called? How do we cascade these individual accumulators? The Freescale 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.

6. What type of memory does this MCU have? What are its memory capacities?
Kernel RAM (12K)
Kernel stacks, buffers, task area - 4K
Kernel hash array, buffers - 8K

Kernel EEPROM (640 bytes)
Kernel vectors and structures - 640 b

Processor Registers (1K)
Kernel/HCS12 Hardware Registers - 1K

Kernel Flash (128K)
Common Kernel Code - 16K
Kernel Code - 112K

Application RAM (26K)
Application data and task areas - 2K
Application data and task areas - 8K
Application data 16K

Application Non-Write-Protectable Shadowed RAM (144K)
Application paged RAM /or Heap area for FORTH_ARRAYs - 144K
Default Forth DP & NP after COLD restart - 8K

Application Write-Protectable Shadowed RAM (320K)
Application code and data (Write protect region 1 = pages 00–0F) (Write protect region 2 = pages 10–13) - 320K

Application EEPROM (384 bytes)
EEPROM Variables - 384 b

Application Flash (384K)
Application code, device drivers - 384K

Shadow Flash (480K)
Transparently backs-up RAM - 480K

7. How many index registers does it have and what are they called? A
– A one-byte (8-bit) general purpose register.
– Since many mathematical operations can be performed using A, it is also referred to as the A accumulator.

B
– A one-byte (8-bit) general purpose register.
– Since many mathematical operations can be performed using B, it is also referred to as the B accumulator.

D
– A two-byte (16-bit) general purpose register.
– The D register is actually the concatenation of the A and B registers. – A is used as the more significant byte with B as the less significant byte. – Note, the two bytes worth of registers may be used as either A and B or as D, but not both at the same time.

X
– A two-byte (16-bit) register primarily used to hold addresses. Very few mathematical operations can.
Index Registers and Others

Y
– A two-byte (16-bit) register primarily used to hold addresses. Very few mathematical operations can.

SP
– A two-byte (16-bit) register used to manipulate the stack data structure.

PC
– Called the program counter, this is a two-byte (16-bit) register that holds the address of the next instruction to be executed. CCR
– The condition code register maintains general operating status of the processor and some information used for branching....
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