The architecture of COSMAC (Complementary-Symmetry Monolithic-Array Computer) provides an adequate but small instruction repertoire, emphasizes a strong input/output capability, and is organized to minimize the amount of external logic needed to build up a complete computer. Its heart is a 16x16 scratch pad; any reference to memory is made via one of these 16 registers. Addressible memory is 65,536 8-bit bytes. An eight-bit two-way data bus interconnects the processor, any mixture of RAM and ROM, and the peripheral devices. The CPU presents a 40-pin interface to the system;: the 8-bit data bus; eight lines for multiplexing out 16-bit addresses to RAM or ROM, clock, reset, and load controls; two signals to control memory read and write; three lines to signal the state of the CPU (fetching or executing an instruction, responding to interrupt or direct-memory-access request); two time pulses per machine cycle for peripheral logic use; four lines driven during execution of the input/output instruction; four external flags from the peripherals; three request lines, respectively, for interrupt, DMA in, DMA out; and three power lines, one of which defines the interface high signal level.

CPI-279		Understanding CMOS
MPL-200		RCA Microsystems 1800 Product Guide and Price List
MPM-102		Program Development Guide for the COSMAC Microprocessor
MPM-109		COSMAC Microtutor Manual
MPM-201C		User Manual for the CDP1802 COSMAC Microprocessor
MPM-202A		Timesharing Manual for the RCA CDP1802 COSMAC Microprocessor
MPM-206A		Fixed-Point Binary Arithmetic Subroutines for RCA COSMAC Microprocessors
MPM-207		Floating-Point Arithmetic Subroutines for RCA COSMAC Microprocessors
MPM-209		COSMAC Microtutor II Manual
MPM-212		Instruction Manual for RCA COSMAC Microterminal
MPM-217		RCA COSMAC Floppy Disk System II CDP18S805 Instruction Manual
MPM-224		Instruction Manual for the RCA COSMAC Evaluation Kit CDP18S020 and the EK/Assembler-Editor Design Kit CDP18S024
VIP-330		RCA COSMAC VIP Instruction Manual for VP-111
VIP-565		VIP EPROM Programmer VP565 Instruction Manual

Programmer's Guide to the 1802, Tom Swan, Hayden Publishing, 1981

Handbook of Microprocessors, Microcomputers, and Minicomputers, John D. Lenk, Prentice-Hall, 1979

I've scanned several articles from 1970's-era issues of RCA Engineer magazine. You can see the scans here.

[RCA] Solid State Division's microprocessor business is built around the CDP1802 microprocessor, a CMOS implementation of Joe Weisbecker's COSMAC architecture, which is radically different from the Intel and Motorola architectures. COSMAC was specifically developed to minimize logic complexity, allow very compact programs, and interface efficiently with the outside world. This lower complexity permits us to manufacture the CDP1802 in CMOS at a cost comparable to NMOS and PMOS competition with its more complicated logic. And Solid State Division is able to compensate for its late start in this business by capitalizing on the well-known electrical benefits of CMOS technology - low and flexible power requirements, unexcelled noise immunity, and tolerance to wide temperature extremes.

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The manuals in this particular box are actually the same core text, just different covers and title pages. This COSMAC Microtutor Manual was written by J. A. Weisbecker at RCA Laboratories in Princeton, New Jersey and has the following Foreward:

Computers can be large, complicated, expensive, and hard to understand. MICROTUTOR is a computer that is small, simple, inexpensive, and easy to understand. It comprises 256 words of memory, input switches, a two-digit output display, and the RCA COSMAC microprocessor. Contrary to popular belief, computers are quite simple in concept and fun to play with. They can be useful but we'll try not to dwell on this aspect in deference to more sensitive readers. A word of caution, if MICROTUTOR makes computers seem simple to you, don't tell anyone. You can earn more money perpetuating the computer complexity myth. Readers who insist on knowing every last little detail about COSMAC should refer to the RCA COSMAC MICROPROCESSOR MANUAL. Readers who want to be protected from actual computer hardware by software aids with names like assembler, interpreter, simulator, and compiler should save up their money for a more expensive system.

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 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 RCA Microtutor II (CDP18S012), introduced in 1977, is similar to the more common COSMAC Elf. Programs are entered via toggle switches and a two-digit LED display serves as the output device. The Microtutor has a pair of expansion connectors (RCA refers to these as External Option Sockets), into which optional boards can be inserted. Eight switches along the bottom allow direct entry of a hexadecimal value. A pushbutton switch IN enters the value. Three more switches provide MP (Memory Protect), LD (Load) and RN (Run) functions.
	The CDP1802CD microprocessor with what looks like a date code from 1977.
	This is a 256 byte (yes, byte) RAM expansion card.

The following announcement appeared in the May-June 1978 issue of Creative Computing magazine:

RCA COSMAC Microtutor II

Intended especially for engineers, students, and hobbyists who wish to understand and use microprocessors, RCA Solid State's COSMAC Microtutor II, CDP18S012, is a complete basic microcomputer system available for quick and easy hands-on operating and programming experience. The new RCA COSMAC Microtutor II, preassembled and containing its own regulated power supply, is based on the RCA CDP1802 CMOS 8-bit microprocessor and supersedes the original Microtutor CDP18S011. The new CDP18S012 provides input via eight binary toggle switches and output on two seven-segment LED hexadecimal digit displays plus a Q LED output. Additional toggle switches are provided for all the required controls to examine and alter memory locations and to initiate program execution. Microtutor II is provided with 256 bytes of CMOS RAM on a memory card which attaches to the base through a standard 44-pin connector. Microtutor II has a crystal clock for stabilized timing applications and a memory protect switch which inhibits the memory write operation to prevent an improperly running program from writing into itself. $195.

For further information and copies of the Product Description PD9: RCA Solid State Division, Box 3200, Somerville, NJ 08876, or from RCA Solid State distributors.

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Type Nomenclature
Suffix	Description
CD	4-6.5V, ceramic package
CE	4-6.5V, plastic package
D	4-10.5V, ceramic package
E	4-10.5V, plastic package
CH	4-6.5V, chips
CW	4-6.5V, chips in wafer form