M7013

This document is an Engineering Change Order Log detailing various modifications and corrections made to the M7013 Vector and Character Generator Control module for VT40, which is part of the PDP-11 Family.

The log covers a series of engineering changes issued between November 1972 and October 1973, addressing different problems with the module:

1. Initial Design & Manufacturing Flaws (M7013-B0001, M7013-B0002): Early changes focused on correcting fundamental module etch errors, fixing incorrectly ordered Character ROMs, and bringing the module up to a corrected "B" etch revision. These changes often required exchanging existing modules for reworked ones, and M7013-B0002 specifically aimed to incorporate all current engineering changes into this "B" revision, involving backplane modifications and prerequisite FCOs.

2. Functional & Logic Errors (M7013-B001A, M7013-A0004): Later ECOs addressed specific operational bugs. M7013-B001A corrected a logic failure occurring when a line feed instruction preceded a zero-length vector instruction, and also added necessary split lugs for coax cables on new "B" etch revisions. M7013-A0004 fixed a clocking error that could cause issues after a system resume, requiring detailed wiring changes for both "A" and "B" etch revision modules.

3. Reset and Testing Issues (M7013-00003, M7013-0003A, M7013-0003B): A significant problem was identified where the module could not be completely reset, leading to issues in XOR testing (M7013-00003). This necessitated a major rework of all "B" boards and a relayout to a new "C" etch revision. Related ECOs (M7013-0003A, M7013-0003B) provided specific etch and wiring corrections for character output register clocking and other wiring errors.

Overall, the document provides a historical record of hardware updates, reworks, and board exchanges implemented to resolve design flaws, improve functionality, and enhance the reliability and testability of the M7013 module in the field and during manufacturing.