Hello, I have just finished it. 
I hope you can enjoy the project at ygg-it.tripod.com. You may leave in this forum your comments if you like. Thanks.
APOLLO181 is a homemade didactic CPU made of bipolar logics and memories, characteristic of the TTL Bugbook® era in 1970s
APOLLO181 has been conceived and assembled in Italy in 2012 by Gianluca G. (author of the homemade Z80/AM95 microcomputer) using early 1970s TTL technology. Designed and tested with the aid of a hardware simulator, APOLLO181 is running today at 2.5 MHz on a 12x12 inches single perfboard.
The design is based on the famous 74181 chip that is a TTL Arithmetic and Logic Unit.
APOLLO181 uses 8-bit instruction word and 8-bit address bus which can access 256 Byte of user program memory. The reason we can classify it a 4-bit processor is that the internal registers and the arithmetic logic unit perform computation on 4-bit (or nibble) intermediate results: advantages of a shorter word are simpler circuits and higher speeds.
The instruction set consists of sixteen basic commands which perform input and output interfacing, conditional jumps and operations like addition, subtraction, increment, decrement, shift operand, magnitude comparison, Exclusive-OR, AND, NAND, OR, NOR on 4-bit data words.
APOLLO181 is a multi-chip board and its peculiarity is that all the employed TTL components were described in the Bugbook® I & II (LOGIC & MEMORY EXPERIMENTS USING TTL INTEGRATED CIRCUITS, written by Dr. Peter R. Rony © 1974, 1st edition), as a Gianluca G.'s personal tribute to these books. By happy coincidence we are also approaching the 40 years Bugbook® publication anniversary.
I hope you can enjoy the project at ygg-it.tripod.com. You may leave in this forum your comments if you like. Thanks.APOLLO181 is a homemade didactic CPU made of bipolar logics and memories, characteristic of the TTL Bugbook® era in 1970s
APOLLO181 has been conceived and assembled in Italy in 2012 by Gianluca G. (author of the homemade Z80/AM95 microcomputer) using early 1970s TTL technology. Designed and tested with the aid of a hardware simulator, APOLLO181 is running today at 2.5 MHz on a 12x12 inches single perfboard.
The design is based on the famous 74181 chip that is a TTL Arithmetic and Logic Unit.
APOLLO181 uses 8-bit instruction word and 8-bit address bus which can access 256 Byte of user program memory. The reason we can classify it a 4-bit processor is that the internal registers and the arithmetic logic unit perform computation on 4-bit (or nibble) intermediate results: advantages of a shorter word are simpler circuits and higher speeds.
The instruction set consists of sixteen basic commands which perform input and output interfacing, conditional jumps and operations like addition, subtraction, increment, decrement, shift operand, magnitude comparison, Exclusive-OR, AND, NAND, OR, NOR on 4-bit data words.
APOLLO181 is a multi-chip board and its peculiarity is that all the employed TTL components were described in the Bugbook® I & II (LOGIC & MEMORY EXPERIMENTS USING TTL INTEGRATED CIRCUITS, written by Dr. Peter R. Rony © 1974, 1st edition), as a Gianluca G.'s personal tribute to these books. By happy coincidence we are also approaching the 40 years Bugbook® publication anniversary.
