Components:

• 4004 4-Bit Central Processor Unit (CPU)
  
• 4003 10-Bit Serial-in/Parallel-out, Serial-out Shift Register
  
• 4002 320-Bit RAM and 4-bit output port
  
• 4001 256 x 8-Bit Mask Programmable ROM and 4-bit I/O
  

Features of the MCS-4

• 4-bit parallel CPU with 45 instructions
  
• Sixteen 4-bit general purpose registers
  
• Nesting of subroutines up to 3 levels
  
• Instruction Set includes conditional branching, jump to subroutine and indirect fetching
  
• Directly drives up to:
  
• 4K by 8 of ROM (16 4001's)
  
• 1280 by 4 of RAM (16 4002's)
  
• 128 I/O lines (without 4003's)
  
• Unlimited I/O lines (with 4003's)
  
• Minimum system: CPU and one ROM
  

Each MCS-4 circuit constitues a basic standard building block which allows the design of many different types of systems which can be fabricated using the same parts. The only custom part is the ROM chip which will store a microprogram defined by the user and requires a metal mask option for each new program.

The CPU contains the control unit and the arithmetic unit of a general purpose microprogrammable computer. The ROM stores microprograms and data tables, the RAM stores data and instructions, and the Shift Register is used in conjunction with I/O devices to effectively increase the number of I/O lines.

The MCS-4 set has been designed for optimum interfaceability; the CPU communicates with the RAM's and ROM's by means of a 4-line data bus. This single data bus is used for all information flow between the chips except for control signals which are sent to RAM and ROM over 5 additional lines. One CPU controls up to 16 ROM's (4K x 8 words), 16 RAM's (1280 x 4 words), and 128 I/O lines without requiring any interface circuit. With the addition of few gates up to 48 ROMS & RAMS combined and 192 I/O lines can be controlled by one CPU.

The I/O function, although different from the ROM and RAM functions, is physically located in the ROM and RAM chips. Each 4001 and 4002 has 4 I/O lines for communication with I/O devices.

4001-ROM - The 4001 is a 2048 Bit metal mask programmable ROM providing custom microprogramming capability for the MCS-4 micro computer set. Each chip is organized as 256 x 8 bit words which can be used for storing programs or data tables. Each chip also has a 4 bit input-output (I/0) port which is used to route information to and from the data bus lines in and out of the system.

4002-RAM - The 4002 performs two functions. As a RAM it stores 320 bits arranged as 4 registers of twenty 4-bit characters each. As a vehicle of communication with peripheral devices, it is provided with 4 output lines and associated control logic to perform output operations.

4003-SR - The 4003 is a 10 bit Serial-in/parallel-out, serial-out shift register. Its function is to increase the number of output lines to interface with I/O devices such as displays, printers, switches, etc.

Additional Notes

The .schematic file only contains the 4003 ( 10-Bit Serial-in/Parallel-out, Serial-out Shift Register)