i4003 serial-in parallel-out shift-register

Description

A standalone demonstration of the i4003 shift register circuit.

The i4003 chip is a simple 10-bit serial-input parallel-output shift-register. Manufactured in the same PMOS process technology as the other MCS4 chips, it provided an easy means to add output-ports to a MCS4 system. Typical applications were the control of multiplexed keypads and displays, and the control of general peripheral devices.

Click the input switches or type the 'c', 'e', and 'd' bindkeys to control the clock, enable, and data-input signals. The data is latched and shifted on the rising-edge of the clock signal while the enable input is high. When enable is low, the outputs are de-asserted (weak high), but clock-pulses will still shift the register contents.

Note that it is possible to cascade multiple i4003 chips into a chain via the serial_out output and data_in input. With the data_in input of the first i4003 chip to one I/O port of the i4001 or i4002 chips, and the clock inputs of all i4003 chips connected to another I/O port, an arbitrary bit pattern can be written to the i4003 chip outputs under software control.

See also:

• Overview of the MCS4/i4004 microprocessor system.
• Rekonstruktion und Visualisierung von Systemen mit Intel 4004 Prozessor, p.32-35.

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