Changeset c523a67 in buchla-emu

Timestamp:

12/31/2017 08:37:44 PM (7 years ago)

Author:

Thomas Lopatic <thomas@…>

Branches:

master

Children:

49efb91

Parents:

f0af168

Message:

Updated FPU info.

File:

• readme.txt (modified) (6 diffs)

readme.txt

@@ -276 +276 @@
 -----------------
 
-Here's what we emulate:
+Here's what we currently emulate:
 
   * Motorola 68000 CPU. This is actually the Musashi CPU emulator by
@@ -283 +283 @@
       https://github.com/kstenerud/Musashi
 
+  * Intel 82716: Video chip.
+
+  * Epson SED1335: LCD controller.
+
+  * Western Digital WD1772: Floppy disk controller.
+
+  * Rockwell R65C52: Serial console and MIDI ports.
+
   * Motorola MC6840: Timers.
 
-  * Rockwell R65C52: Serial console and MIDI ports.
-
-  * Epson SED1335: LCD controller.
-
-  * Intel 82716: Video chip.
+  * Unknown item #1: A program running on a microcontroller. It
+    converts the analog signals from the Buchla's controller pads to
+    digital values.
+
+    Neither the program, nor the microcontroller are known, but the
+    protocol (known from the firmware source code) is pretty simple
+    and self-explanatory.
+
+The next development milestone will hopefully emulate the following
+additional components:
 
   * National Semiconductor LMC835: Equalizer.
@@ -297 +310 @@
     to the above equalizer chip.
 
-  * Western Digital WD1772: Floppy disk controller.
-
-  * A few LEDs.
-
-  * Item X: A program running on a microcontroller. It converts the
-    analog signals from the Buchla's controller pads to digital
-    values.
-
-    Neither the program, nor the microcontroller are known, but the
-    protocol (known from the firmware source code) is pretty simple
-    and self-explanatory.
-
-  * Item Y: The actual sound generator, referred to by the firmware
-    source code as "the FPU." This could actually be two chips:
-
-      1. One chip, maybe a DSP, for generating the 15 different
+  * A few indicator LEDs.
+
+  * Unknown item #2: The actual sound generator, referred to by the
+    firmware source code as "the FPU." This is the biggest unknown so
+    far. Judging from the firmware source code it consist of two
+    parts:
+
+      1. The function generator that generates the 15 different
          parameter envelopes for each of the 12 voices:
 
@@ -327 +332 @@
            - 1x Output signal stereo location.
 
-           - 1x "Dynamics." (TBD - currently not emulated.)
+           - 1x "Dynamics" - whatever that is.
 
          Over time, the chip interpolates between the points of the
          envelopes drawn in the MIDAS VII instrument editor.
 
-      2. A second chip for the actual sound generation. This is likely
-         a DSP.
+      2. The digital oscillator.
 
          XXX - Details to be filled in.
@@ -343 +347 @@
          Obviously, the emulator does everything digitally.
 
-    This "two chip" hypothesis would be in line with the "four
+    This "two part" hypothesis would be in line with the "four
     computers" marketing claim from the Buchla 700 marketing copy. The
     four "computers" would be the Motorola 68000, the microcontroller
-    that does the A/D conversion of the pad inputs, plus the two CPUs
+    that does the A/D conversion of the pad inputs, plus the two parts
     that constitute "the FPU."
+
+    The firmware source code archive indicates that the FPU is based
+    on micro-programmable hardware. We recently ran this by Lynx, the
+    developer of the firmware, who generously agreed to meet up with
+    us in Oakland, CA. While he never worked on the FPU and thus was
+    not familiar with its implementation details, he was able to
+    confirm that the FPU was based on AMD's Am2900 family.
 
 If you have access to an actual Buchla 700, please do contact us. It
@@ -353 +364 @@
 
 If your Buchla is non-functional, this is also fine. We might be able
-to gain some insights from reading out the FPU microcode PROMs.
+to gain some insights from reading out the FPU microcode PROMs or from
+figuring out how the FPU chips are wired together.