VAXstation 100 firmware notes - Revision history

Larsbrinkhoff: /* BitBlit Accelerator */ Link to frame buffer.

2024-02-27T06:50:49Z

‎BitBlit Accelerator: Link to frame buffer.

2023-11-16T18:04:14Z

Better cat

2023-03-20T07:02:41Z

‎BitBlit Accelerator: Updated line drawing.

2023-03-19T13:59:11Z

‎BitBlit Accelerator

2023-03-16T13:53:08Z

‎BitBlit Accelerator

2023-03-16T13:06:44Z

‎BitBlit Accelerator: Line drawing.

2023-03-15T11:34:58Z

‎BitBlit Accelerator: Cursor.

2023-03-15T07:57:05Z

‎BitBlit Accelerator: ALU function, tile address.

2023-03-11T16:11:48Z

‎BitBlit Accelerator

2023-03-11T16:10:15Z

‎BitBlit Accelerator

@@ Line 275: / Line 275: @@
 ==BitBlit Accelerator==
-The BBA is a custom [[microcode]]d processor based on the [[Am2901]] family.  It was initially to be an optional add on, but later it was required.  The BBA can access the frame buffer and has its own 256 by 16 bit scratchpad RAM.
+The BBA is a custom [[microcode]]d processor based on the [[Am2901]] family.  It was initially to be an optional add on, but later it was required.  The BBA can access the [[frame buffer]] and has its own 256 by 16 bit scratchpad RAM.
 The 68000 CPU communicates with the BBA through the scratchpad.  When a command has been written, the CPU pokes a hardware register to signal the BBA to start.  The BBA interrupts the CPU when done.

← Older revision		Revision as of 18:04, 16 November 2023
Line 600:		Line 600:
	Line drawing is done with a classic Bresenham algorithm. For each step along the major axis, scratchpad location 02E is added to an accumulator. If the accumulator overflows, the location pair 030,032 is used to update the point on the line, and location 02C is subtracted from the accumulator. Otherwise, 034,036 is used.		Line drawing is done with a classic Bresenham algorithm. For each step along the major axis, scratchpad location 02E is added to an accumulator. If the accumulator overflows, the location pair 030,032 is used to update the point on the line, and location 02C is subtracted from the accumulator. Otherwise, 034,036 is used.

−	[[Category: ~~DEC~~ Software]]	+	[[Category: VAX Software]]

@@ Line 366: / Line 366: @@
 | 32 bits
+|
-| Line bitmap address (start)
+| Line destination bitmap address
 |-
 | 02A
@@ Line 376: / Line 376: @@
 | 16 bits
+|
-| Line major axix
+| Line major axis
 |-
 | 02E
@@ Line 385: / Line 385: @@
 | 030
 | 16 bits
-−
+|
+| Line x delta, when accumulator overflows (see below)
 |-
 | 032
 | 16 bits
+|
-| Line bitmap width in bytes
+| Line address, delta when accumulator overflows
 |-
 | 034
 | 16 bits
+|
+| Line x delta, when accumulator doesn't overflow
 |-
 | 036
 | 16 bits
+|
+| Line address delta, when accumulator doesn't overflow
 |-
 | 038
 | 16 bits
+|
+| Line mask x offset
 |-
 | 03A
 | 32 bits
+|
-| Line bitmap address (origin)
+| Line mask bitmap address
 |-
 | 03E
 | 16 bits
+|
-| Line bitmap width in bytes
+| Line mask bitmap width in bytes
 |-
 | 040
@@ Line 597: / Line 597: @@
 | 1
 |}
 [[Category: DEC Software]]

@@ Line 371: / Line 371: @@
 | 16 bits
+|
-| Line height (including last point, if any)
+| Line steps (optionally including last point)
 |-
 | 02C
 | 16 bits
+|
-| Line delta y
+| Line major axix
 |-
 | 02E
 | 16 bits
+|
-| Line delta x
+| Line minor axis
 |-
 | 030

@@ Line 373: / Line 373: @@
 | Line height (including last point, if any)
 |-
-| 02E
+| 02C
 | 16 bits
+|

@@ Line 306: / Line 306: @@
 | 16 bits
 | 5FAA
-| Source bitmap width in words
+| Source bitmap width in bytes
 |-
 | 00A
@@ Line 321: / Line 321: @@
 | 16 bits
 | 6022
-| Mask bitmap width in words
+| Mask bitmap width in bytes
 |-
 | 012
@@ Line 336: / Line 336: @@
 | 16 bits
 | 3036
-| Destination bitmap width in words
+| Destination bitmap width in bytes
 |-
 | 01A
@@ Line 446: / Line 446: @@
 | 32 bits
+|
+| Cursor source bitmap address
 |-
 | 052
 | 16 bits
+|
+| Cursor source x offset
 |-
 | 054
 | 16 bits
+|
+| Cursor source width in bytes
 |-
 | 056
 | 32 bits
+|
+| Cursor mask bitmap address
 |-
 | 05A
 | 16 bits
+|
+| Cursor mask x offset
 |-
 | 05C
 | 16 bits
+|
+| Cursor mask width in bytes
 |-
 | 05E
 | 32 bits
+|
+| Cursor destination bitmap address
 |-
 | 062
 | 16 bits
+|
+| Cursor destination x offset
 |-
 | 064
 | 16 bits
+|
+| Cursor destination width in bytes
 |-
 | 066
 | 16 bits
+|
+| Cursor mask width
 |-
 | 068
 | 16 bits
+|
+| Cursor mask height
 |-
 | 06A
 | 16 bits
+|
+| Cursor ALU function
 |-
 | 06C
 | 32 bits
+|
+| (Cursor)
 |}
@@ Line 530: / Line 530: @@
 |-
 | 5
+| Draw cursor
 |-
 | 6

@@ Line 351: / Line 351: @@
 | 16 bits
 | 5F98
+| ALU function
 |-
 | 020
 | 32 bits
 | 5FB0
+| Tile address
 |-
 | 024
@@ Line 527: / Line 527: @@
 |-
 | 4
-| Use source halftone
+| Use source tile
 |-
 | 5
@@ Line 537: / Line 537: @@
 | 7
+|
 |}
 [[Category: DEC Software]]

@@ Line 291: / Line 291: @@
 | 16 bits
 | 5F96, 60AC
-| Command mask
+| Command bitmask; see below
 |-
 | 002

@@ Line 277: / Line 277: @@
 The BBA is a custom [[microcode]]d processor based on the [[Am2901]] family.  It was initially to be an optional add on, but later it was required.  The BBA can access the frame buffer and has its own 256 by 16 bit scratchpad RAM.
-The 68000 CPU communicates with the BBA through the scratchpad.  When a command has been written, the CPU pokes a hardware register to signal the BBA to start.  The BBA interrupts then CPU when done.
+The 68000 CPU communicates with the BBA through the scratchpad.  When a command has been written, the CPU pokes a hardware register to signal the BBA to start.  The BBA interrupts the CPU when done.
-The contents and structure of the commands are not yet known.  The first word in the scratchpad is apparently a bit mask indicating various functions to be done.  Data follows.
+The contents and structure of the commands are being reverse engineered.  The first word in the scratchpad is a bit mask indicating various functions to be done.
 Scratchpad locations.