Product Overview
Two Serial Channels On One 40-Pin Motorola Package
Condition
Used, and this is the one piece we have. The photos show the actual chip: a black plastic 40-pin dual in-line package with the Motorola logo and three crisp white marking lines reading MC68681P, 6C98R, and QHPF9404. The leads are straight and evenly spaced across both rows, uniformly bright, with no solder, flux, or board residue visible on any pin. The package top carries the round mold marks and the pin 1 dimple that come from the factory molding process, not from handling. It has not been powered up or functionally tested here, so it is sold untested and the photos are the spec.
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Product Overview
This is a single Motorola MC68681P, the plastic dual in-line version of the MC68681 DUART and a member of the M68000 family of peripherals. The DUART was built to sit directly on the asynchronous 68000 bus, talking to the processor through an 8-bit bidirectional data bus buffer with on-chip interrupt control logic, so a designer got serial capability without a bridge chip in between. Inside are two independent full duplex communication channels, A and B, each with its own receiver and transmitter and its own programmable baud rate selection, plus an on-chip timing logic section, a 6-bit parallel input port, and an 8-bit parallel output port that most designs pressed into service for modem control and handshake lines. The part in these photos is marked MC68681P over 6C98R over QHPF9404; the trailing 9404 reads like a 1994 date code in the usual year-week form, though we are reading a package, not a factory record. Speed grade, operating temperature range, and crystal requirements are not confirmed here - verify against the datasheet before use.
Key Features
- Motorola MC68681P, 40-pin plastic dual in-line package (P suffix)
- Marked MC68681P / 6C98R / QHPF9404 with the Motorola logo, as photographed
- Two independent full duplex asynchronous channels, A and B
- Programmable baud rate selection on each channel
- On-chip timing logic section, one of the eight major blocks in the MC68681
- 6-bit parallel input port and 8-bit parallel output port
- 8-bit bidirectional data bus buffer and interrupt control logic for the asynchronous M68000 bus
- One piece, condition Used, sold untested
- Speed grade and temperature range not confirmed - verify against the datasheet before use
Applications
- A restorer bringing a 68000 single board computer back to life and needing the console and auxiliary serial ports working again
- A maintenance tech pulling a dead DUART off an obsolete industrial controller board where the original Motorola number is the only thing the schematic names
- A homebrew 68k builder who wants two hardware serial ports from one socket instead of stacking separate UARTs
- A retrocomputing collector stocking a spares drawer for M68000 family peripherals that no distributor carries anymore
Frequently Asked Questions
What does the MC68681 actually do on a board?
It handles two independent asynchronous serial channels, each with its own receiver, transmitter, and programmable baud rate, and it adds an on-chip timing logic section plus a 6-bit input port and an 8-bit output port. On most 68000 designs that meant a console port, a second port for a modem or printer, and a handful of control lines from one chip.
Is this the plastic package or the ceramic one?
Plastic. The P suffix on the MC68681P designates the plastic 40-pin dual in-line package, and the photos show a black plastic body with two straight rows of twenty leads.
What are the second and third lines of the marking?
The chip reads MC68681P on the first line, 6C98R on the second, and QHPF9404 on the third. Those lower lines are factory assembly and lot codes; the trailing 9404 follows the common year-week date code pattern for a 1994 part, but we cannot confirm that against Motorola documentation, so treat it as a reading of the package rather than a certified date.
It is listed Used - what am I taking on?
You are taking on the testing. This chip has not been powered up, clocked, or exercised on a bench here, so there is no functional result to quote and no guarantee of speed grade. What you do get is the exact piece in these photos: markings you can read yourself, leads that are straight and clean with no solder or flux on them, and no bent or reworked pins hiding in the row. Look hard at the images before you buy, because they are the whole disclosure. Shipping runs $8 flat rate and goes free once your order passes $28, and orders leave the Idaho warehouse the same or next business day.
Before a 68000 board could say a word to the outside world, something had to turn bytes into baud - and on thousands of them it was this 40-pin Motorola part doing the talking on two channels at once. If your board has gone quiet on channel A, here is the chip that used to answer.
