Changes between Version 12 and Version 13 of TeradriveHardwareNotes

Timestamp:

09/01/2024 07:39:34 PM (5 weeks ago)

Author:

Mike Pavone

Comment:

--

TeradriveHardwareNotes

@@ -19 +19 @@
 
 `000000 - 3FFFFF`: cartridge or expansion port or PC memory or firmware\\
-`400000 - 7FFFFF`: expansion port or cartridge (need to verify what happens here when PC memory or firmware is enabled at 0)\\
+`400000 - 7FFFFF`: expansion port or cartridge or PC memory or firmware\\
 `800000 - 9FFFFF`: unmapped (32X)\\
 `A00000 - A07EFF`: Z80 address space\\
@@ -61 +61 @@
       Window is 8KiB in size and is used for both PC-side access to MD hardware and the Kanji/romdisk ROM\\
 1163: `XXRRXXXX`
-      bit 0: Enables auxiliary ROM on 68K side\\
-      bit 1: Enable 286 memory window into 68K address space (must be clear when booting 68K)\\
+      bit 0: Enables auxiliary ROM (must also be set for 286 window into 68K address space to function)\\
+      bit 1: Enable 286 memory window into 68K address space (also disables access to firmware by 68K)\\
       bit 2: unknown\\
       bit 3: unknown\\
@@ -74 +74 @@
              Clearing bit from 68K side puts 68K into reset and releases 286\\
              Making certain other reg changes seems to make clearing this bit have no effect\\
-      bit 1: 0 = Tera drive boot ROM mapped at 0 on 68K, 1 = cart mapped at 0\\
+      bit 1: 0 = Teradrive hardware at 0 (if also enabled elsewhere), 1 = cart mapped at 0\\
       bit 2: Controls video switch - 0 = PC video, 1 = MD video\\
       bit 3: Dual boot bit. When both this and bit 1 are set, bit 0 is ignored and both CPUs run independently.\\
@@ -81 +81 @@
       bit 6: Set on TMSS failure immediately before wedging 68K by reading from VDP while configured for writes\\
       bit 7: Seems to start as 1, clearable on 68K but not on 286\\
+      Dual boot mode makes all Teradrive hardware except AE000X and A14000 inaccessible (no !DTACK)
 1165: `0000RR0R`
       bit 0: Indicates PC/MD switch setting, 0 = MD boot, 1 = PC boot\\
@@ -89 +90 @@
       low bits of selected 8K page for access to 68K memory from 286\\
 1167: `0000XXXX`
-      high bits of selected 8K page for access to 68K memory form 286\\
+      high bits of selected 8K page for access to 68K memory from 286\\
       when taken together with 1166, holds `68K address >> 12`\\
       Also used along with 1166 for passing params from PC side to MD-side firmware\\
@@ -185 +186 @@
 B1 = pin on the front side of the system closest to the drive bays. A1 = pin on the backside also closest to the drive bays
 
-Note: this has not been thoroughly checked. Highly recommend you double-check any pin mappings before relying on this.
-
+This was first [http://piroxilin.narod.ru/sega/teradrive-slots_2.xls documented by piroxolin], but has been independently confirmed.
 {{{
 B1  VCC
 B2  SR2
-B3  VA0
+B3  VA8
 B4  VA11
 B5  VA7