Pyntel4004
A Python software implementation of the Intel 4004 processor.
General Information
- Two pass assembler using the original mnemonics, directives and comments syntax
- Monitor facility to step through code and examine registers, memory etc
Design goals
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[ ] As much of the internals as possible should be carried out using binary arithmetic and operations.
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[ ] No 3rd party libraries to be used (i.e. pure Python).
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[ ] Build a fully-working i4004 opcode emulator.
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[ ] Build a fully-working assembler which generates correct op-codes.
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[ ] Construct a fully-working software-based i4004 chip which can use the
generated object code from the compiler (possibly using micro-python or circuit python on an Ardiuno Board).
Status
18-MAY-2021: Implementing full test suite
21-APR-2021: Instruction Set functionally complete
Entering Testing Phase
Example
Assembler Directives and other additions
Assembler directives are not part of the program itself, but can control things like starting address, and various environmental settings.
| Directive | Example | Meaning |
|---|---|---|
| end | end | Indicating end of program, but not necessarily end of code |
| org | org 100 | Assemble and place object code commencing at address 100 |
| pin | pin 1 | Value of i4004's Pin 10 (test pin) |
| / | / Author: ALS | A comment |
| label, | loop, | A label can be referred to in various control transfer statements. It MUST end in a comma (,) |
Monitor Commands
| Command | Example | Meaning |
|---|---|---|
| "Enter" | "Enter" | Execute the current instruction and move to the next |
| acc | acc | Show the current contents of the Accumulator |
| b n | b 71 | Create a breakpoint at address n |
| carry | carry | Show the current contents of the Carry Bit |
| crb | crb | Show the currently selected RAM Bank |
| off | off | Continue to execute the program with no trace |
| pc | pc | Show the Program Counter |
| pin10 | pin10 | Show the status of PIN10 on the i4004 chip (test pin) |
| q | q | Quit the monitor without executing any further commands |
| ram | ram | Show the complete contents of RAM |
| reg n | reg 7 | Show content of a specified register |
| regs | regs | Show all 16 registers |
| rom | rom | Show the complete contents of ROM |
| stack | stack | Show the stack and the location of the stack pointer |
