RS-232 Serial & Parallel Interface with Expansion Bus Pass-Thru

Combined RS-232 serial and Centronics parallel interface for the Coleco ADAM. Connects via the side expansion port (60-pin card edge). Made in Canada. Shipped with a pre-attached parallel cable, program diskette, and instruction manual. US units included an additional serial cable option requiring user assembly; Canadian consumers could order custom serial cables ($35.00 option).

Key ICs (verified from board photography):

INS2651N (Signetics, 28-pin DIP, date code RB8336) — Programmable Communication Interface (USART). Same 2651 chip family used in the Orphanware SI 1A/B and later in MicroFox's 80-column VGA cards — a recurring workhorse across four decades of ADAM serial peripherals.

MC1489C (Motorola) — Quad RS-232 line receiver for serial input.

MC74HC32 (Motorola) — Quad 2-input OR gate (HC = high-speed CMOS) for control logic.

SN74LS368AN (TI, El Salvador) — Hex inverting tri-state buffer for bus interface.

SN74LS123N (TI) — Dual retriggerable monostable multivibrator for timing/pulse generation.

Crystal oscillator for USART baud rate reference.

Software Integration: Included SmartBASIC drivers (siobasic, bserial, bprinter) and CP/M drivers (cpmptr, cpmser). Under SmartBASIC, output routing is controlled via PR# commands: PR#0 = monitor/TV, PR#1 = ADAM printer, PR#2 = parallel device, PR#3 = serial device. The siobasic program uses SmartKeys to configure serial port parameters (baud rate, parity, etc.). Under CP/M, the cpmptr and cpmser files are transferred to the CP/M system disk for parallel and serial support respectively. Assembly language routines handle USART initialization and are loaded below address 28000 (LOMEM:28000 protects this area).

Connectors: 14-pin serial output (TXD, RXD, RTS, CTS, DCD, GND, DTR — CCITT V.24 compliant) and 26-pin Centronics-compatible parallel output. Full CCITT V.24/EIA RS-232C interface documentation included in manual.