Cμ4 four-bit CPU

It refers to 4-bit CPU projects with discrete logic such as TD4-CPU and Cute-CPU, improves the previous instruction and machine code encoding methods, reduces the size, and simplifies the structure of a 74-chip discrete CPU product.
A set of this CPU consists of the mainboard (CPU) and an expansion board (button, dot matrix, 1602, etc.). You can write simple assembly programs for simple human-computer interaction.
 
The basic parameters are as follows:
Power supply: +5V or +7.5~+12V
Operating current: 600mA (standard TTL)/200mA (H-CMOS)
Clock frequency: manual/built-in IRCROM: 4k x 8bit; RAM: 1k x 4bit; I/O : 16 x 4bit (4-bit address line); register group: ACC (main operand), B (secondary operand), C register, three addressing registers A2, A1, and A0.
Can address 4kB of program space or 1kB of RAM. IO port addressing is completed independently by the A0 register. Built-in fixed IRC oscillator without stack
, clock frequency ≥1KHz; you can also select buttons to input clock pulses. The operation part is built around 74LS181 and has two flag registers, CF and ZF. The basic instructions are all single-cycle: addition, subtraction, negation, exclusive OR, identical OR, bitwise AND, comparison, data transfer, immediate data storage in register, IO input and output, RAM access, jump, PSW conditional jump wait.
The basic structure is as follows:
 
Compared with similar products (TD4, Cute, etc. CPU), this design can be connected to an external display/button array, etc. The IO port of the motherboard reads and writes peripherals with standard 6800 bus timing (4-bit data); this is very convenient. To a great extent, it makes up for the shortcomings of TD4-CPU in human-computer interaction, improves the shortcomings of Cute-CPU with few external expansion IO ports, and effectively improves the user experience.
 
Before use, you need to write the netlist file corresponding to GAL1-4 to the corresponding GAL16V8, and then plug it into the board before the machine can be used.
For detailed instructions, please see the attached introduction document and related machine code.
 
The motherboard picture is as follows:
 
The 3D preview of the motherboard is as follows:
 
LCD1602 lights up preview: