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The RCA CDP1802 COSMAC microprocessor is a one-chip CMOS 8-bit
register-oriented central processing unit introduced in 1976.
The 1802 was first popularized in a 1976 Popular Electronics article that described the "COSMAC Elf" computer. Around the same time commercial companies began offering similar products based on the 1802. The 1802 is interesting for a number of reasons, not the least of which is the fact that it uses static CMOS circuitry, meaning it has no minimum clock frequency. Also, most instructions execute in two clock cycles. It has sixteen general purpose registers, each of which are 16 bits wide. Any of these registers can be used as a program counter or an accumulator.
I am interested in collecting and preserving systems and documentation related to the 1802 microprocessor. If you have any equipment, manuals, parts or other items related to the 1802, please send me an e-mail!
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RCA produced a number of documents related to the COSMAC series of processors.
Programmer's Guide to the 1802, Tom Swan, Hayden Publishing, 1981 Handbook of Microprocessors, Microcomputers, and Minicomputers, John D. Lenk, Prentice-Hall, 1979
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The following two pages of CDP 1802 microprocessor data sheets are
taken from CMOS 1800-Series LSI
Product Selection Guide (MPG-180D) from RCA Solid State.
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The main board contains the "user interface" equipment, including eight
input toggle switches, a Load (LD) switch and pushbuttons for
Input (IN), Clear (CL) and Start/Step (ST).
The output is a pair of hexadecimal LED displays. The main board also contains three sockets, for a Memory Card (M), COSMAC Card (P), and an External Option (E). |
The plug-in COSMAC CPU card contains the two integrated circuits that
make up the 1801 processor, introduced in 1975.
The chip on the left is a CDP 1801 CRD ("Microprocessor Register") and provides the Arithmetic Logic Unit (ALU) functions. The chip on the right is a CDP 1801 CUD ("Microprocessor Control") and provides control and sequencing functions. It supports 59 op codes. The subsequent CDP1802, introduced in 1976, combined the functionality of these two chips into a single deivce, as well as adding instructions. |
The plug-in memory card provides 256 bytes of Random Access Memory (RAM).
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| Click here for an in-depth magazine article on the Microtutor from 1976. |
The following announcement appeared in the May-June 1978 issue of Creative Computing magazine:
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You can see more photos by clicking here. |
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Netronics in Connecticut also offered a COSMAC system. This is
an advertisement from the May-June 1978 issue of
Creative Computing magazine.
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The 1802 also shows up in some unexpected places, like this
battery-powered hand-held unit.
Click here for more information and photos. |
| Click here for a 1974 article discussing the use of the COSMAC microprocessor in a system with communications links, floppy disks, and a television display. |
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Updated February 2, 2008