My company's reputation was tarnished when my customer's lead technician tried to score points by demanding a complete technical data package (TDP) for a PCB iteration before it was fully completed. Problem was, the TDP, which was never supposed to see the light of day, had errors.
In a fit of youthful enthusiasm -- long before iPads or even laptops -- two coworkers and I left our steady paychecks behind to establish an entrepreneurial technical services company. We had kept a good relationship with our former employer, which won us design and management work. Our customer had long manufactured mobile data terminals (MDT) and I had been the lead electronics engineer on a completely redesigned version. The MDTs were networked through modified voice two-way VHF radio systems and were used nationwide by public safety organizations like EMS, fire, police, and sheriffs' departments. We were delighted when our customer decided to introduce a low-cost version of the MDT and asked us to design its electronics.
The requirements seemed simple enough. They were to interface about 20 keys for operator entry and either a two-line vacuum florescent display or two-line liquid crystal display (LCD). The logic board was cost-limited to $50. The customer specified the keyboard and displays. Firmware customization for specific MDT customers was required, and custom runs could be short. The new MDT was to be used with a separate intelligent modem the customer was developing, so the MDT logic board only needed a single serial communication link.
Our customer developed the MDT enclosure and defined our PCB dimensions. Our deliverables would include working prototypes, PCB artwork with drawings, schematic and mechanical drawings, a bill of materials with procurement specifications, and any software or firmware documentation. The full documentation collection was called the technical data package or TDP.
To satisfy the $50 limit I decided to use a single chip microcontroller with EPROM. Since our customer favored Intel products, the 8051/8751 microprocessor seemed like a good choice. It had an on-chip serial interface, and its parallel ports could handle the keyboard and the display. I designed a PCB using the 8751 EPROM variant. It was accepted by the customer. Then the trouble started.
On ordering parts for the prototype I discovered that the $8 catalog price for the 8751 I had found during design was a misprint. Intel assumed that their 8751 would be used only for development, so they priced the EPROM 8751 at about $70 each! The whole budget was blown by a single bad part choice and my failure to double check my procurement source. We went ahead and demonstrated the 8751 board while I feverishly searched for an affordable alternative. Salvation came in the form of a Philips part, the 87C451.
It was available with a one-time programmable EPROM. It also had all the features of the Intel 8051, plus two additional parallel ports. Thankfully its price tag was under $8. The package was different: the 8051 used a rectangular 40-pin dual in-line package, while the Philips 87C451 used a square 68-pin plastic leaded chip carrier -- but it would fit. It was redesign time.