From 6ca3b9281018c4ec309b62e42b6de3433e883b01 Mon Sep 17 00:00:00 2001 From: Andrew Makousky Date: Sat, 8 Aug 2020 18:52:47 -0500 Subject: [PATCH] Document "*EXT.DTK" signal properly. PDS slot pinouts have now been verified, remove TODO note. --- hardware/fpga/bbu/README.md | 10 +++++- old_artifacts/schems/README.md | 7 ++-- old_artifacts/schems/retrace_se_mlb_p1.svg | 37 +++++++++++----------- 3 files changed, 30 insertions(+), 24 deletions(-) diff --git a/hardware/fpga/bbu/README.md b/hardware/fpga/bbu/README.md index 0e3efd9..e2e1f70 100644 --- a/hardware/fpga/bbu/README.md +++ b/hardware/fpga/bbu/README.md @@ -100,12 +100,20 @@ only simple, single-pin interfaces. Peripheral device signals, input or output? -* `*ENTD1K` is very likely an input signal, for PDS use. Why? The +* `*EXT.DTK` is very likely an input signal, for PDS use. Why? The Macintosh Classic is essentially a stripped-down Macintosh SE that uses the same BBU. In that schematic, pin 11 is indicated as connected to a pull-up resistor. So, clearly this must be an input since it cannot be connected. + Actually, the full purpose is documented right here. If this pin is + pulled low, then the system expansion card is responsible for + generating the `*DTACK` signal to indicate to the CPU that the data + transfer is complete. The BBU puts the signal in a high-impedance + state. + + 20200808/https://web.archive.org/web/20190909060927/http://www.ccadams.org/se/pinouts.html + * `*EAREN` is very likely an output signal (also for PDS use), for the reason it is not indicated in the Bomarc Macintosh Classic schematics, i.e. it could be disconnected entirely. diff --git a/old_artifacts/schems/README.md b/old_artifacts/schems/README.md index e791e8c..34569e4 100644 --- a/old_artifacts/schems/README.md +++ b/old_artifacts/schems/README.md @@ -22,11 +22,8 @@ included to reproduce the processing steps. Notes related to the accuracy of the retrace. -* The pinouts of all integrated circuit components and the RAM SIMMs - have been verified with second sources. - -* The pinouts of the PDS slot have **not** yet been verified with - second sources. +* The pinouts of all integrated circuit components, the RAM SIMMs, and + the PDS slot have been verified with second sources. * The resistor values have been checked to be consistent with the reference designators, but **not all reference designators** have diff --git a/old_artifacts/schems/retrace_se_mlb_p1.svg b/old_artifacts/schems/retrace_se_mlb_p1.svg index f6e5f40..9a252ef 100644 --- a/old_artifacts/schems/retrace_se_mlb_p1.svg +++ b/old_artifacts/schems/retrace_se_mlb_p1.svg @@ -60,16 +60,16 @@ inkscape:pageopacity="0.0" inkscape:pageshadow="2" inkscape:zoom="1" - inkscape:cx="897.18755" - inkscape:cy="466.4755" + inkscape:cx="699.39436" + inkscape:cy="485.21248" inkscape:document-units="mm" inkscape:current-layer="layer1" showgrid="false" units="in" - inkscape:window-width="1853" - inkscape:window-height="1025" - inkscape:window-x="67" - inkscape:window-y="27" + inkscape:window-width="1680" + inkscape:window-height="986" + inkscape:window-x="0" + inkscape:window-y="0" inkscape:window-maximized="1" inkscape:snap-global="false" />