Programming the Motorola 68HC11 Lab

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Programming the Motorola 68HC11 Lab

Objectives:

1. To become familiar with programming the Motorola 68HC11 microcontroller, timing diagrams, machine cycles, state diagrams and prepare the student for parallel bus processing.

Materials:
1. Logic Analyzer
2. 68HC11 Trainer

Procedure:

1. Code in the following program using the following steps. Use the Increment Contents of Memory source statement machine language program below as a guide.

mm

EF00
↓
EF0C

Data
↓
Data

2. Block fill memory with 00, so you have the following: BF C100, C1FF, 00

3. Dump the memory locations to check and verify the data stored in: MD C100, C1FF

4. Modify the memory locations with: (MM 20 C1 and MM 21 01)

5. Now set the break points at: BR EF0C and set the break instructions to the last memory location

6. Run the program: g EF00, make sure you start the program at the beginning of the programmed sequence.

Figure 1: 68HC11 Pinout

Increment Contents of Memory Source Statement

Program Description:
Fills a 256 byte block of memory with incremented values. The lowest address (START_ADR) of the block contains '00', the next higher address contains '01', and so on. Note: START_ADR is variable; it is initialized in RWM before execution.

Results:
(START_ADR) = '00', (START_ADR + 1) = '01' ... (START_ADR + FE) = 'FE' (START_ADR + FF) = 'FF'

Alters:
ACCB, IX, SP, CCR

Code:

Lable:

Explanation:

(SP) ← $00F0 Initialize SP away from program and data memory

IXH ← (START_ADR) = ($20), IXL ← (START_ADR +1) = ($21) Initialize IX with the starting address of the block to be filled. IX will always point at teh next address to fill.

ACCB will contain the next value to write out to memory. The first value written is '00'. ACCB ← '00'

Write the next value out to the next address of the block (IX) ← (ACCB)

Point IX at the next address to write to IX ← (IX + 1)

ACCB contains the next value to write to memory ACCB ← (ACCB + 1)

If (ACCB) ≠ then all values have not been written, so branch and write another. If ACCB ≠ 0 then PC ← WR_AGAIN otherwise (PC) = FINISHED

If get here then all 256 bytes are written, stay here.

7. Demux 68HC11 Bus Format Notes:

- Master Clock J↓
- Slave Clock K↓
- Pod 1 = Clock
- Pod 2 = Master/Slave (demux)

Lables:
ADR
ADDR
DATA

Pod 1:
7 .. 0
7 .. 0
xxxxxxxx

Pod 2:
15 .. 8 (hi byte)

xxxxxxxx

Lab Notes
Lab Notes Page 1
Lab Notes Page 2

Lab Data
Figure 2: Timing Waveform, EF00 - EF07
Figure 3: Timing Waveform, EF06 - EF0A
Figure 4: Timing Waveform, EF0A - END
Figure 5: Machine State List

Electrical Engineering lab key words: Microcontroller programming, memory stack, ROM, 68HC11, 68HC11A1, 68HC12, memory configuration, timing diagram, machine cycle, state machine, state diagram, data bus, machine language, code, data locations, pin out, sequential, byte, bit, LSB, MSB, addressing, operation, clock cycle.

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