Support chips 4001: 256-byte ROM (256 8-bit program instructions) and one built-in 4-bit I/O port. A 4001 ROM+I/O chip cannot be used in a system along with a 4008/4009 pair.IMPORTANT section at page 25: http://www.intel.com/Assets/PDF/Manual/msc4.pdf. 4002: 40-byte RAM (80 4-bit data words) and one built-in 4-bit output port; the RAM portion of the chip is organized into 4 "registers" of 20 4-bit words: 16 data words (used for mantissa digits in the original calculator design), accessed in a relatively standard manner, 4 status words (used for exponent digits and signs in the original calculator design), accessed using I/O type commands in place of the ROM's input channel. 4003: 10-bit parallel output shift register for scanning keyboards, displays, printers, etc. 4008: 8-bit address latch for access to standard memory chips and one built-in 4-bit chip-select and I/O port. 4009: program and I/O access converter to standard memory and I/O chips. 4269: keyboard/display interface. 4289: memory interface (combined functions of 4008 and 4009).
Support chips 4001 256-byte ROM (256 8-bit program instructions) and one built-in 4-bit I/O port A 4001 ROM+I/O chip cannot be used in a system along with a 4008/4009 pairIMPORTANT section at page 25 http//wwwintelcom/Assets/PDF/Manual/msc4pdf 4002 40-byte RAM (80 4-bit data words) and one built-in 4-bit output port; the RAM portion of the chip is organized into 4 "registers" of 20 4-bit words 16 data words (used for mantissa digits in the original calculator design) accessed in a relatively standard manner 4 status words (used for exponent digits and signs in the original calculator design) accessed using I/O type commands in place of the ROM's input channel 4003 10-bit parallel output shift register for scanning keyboards displays printers etc 4008 8-bit address latch for access to standard memory chips and one built-in 4-bit chip-select and I/O port 4009 program and I/O access converter to standard memory and I/O chips 4269 keyboard/display interface 4289 memory interface (combined functions of 4008 and 4009)