Difference between revisions of "VAXstation 100 firmware notes"

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(→‎D0 flags: Bit 28 seems to be for host attention, even though it's set from the TRAP #1 exception vector.)
(Add RAM memory map as used by ROM.)
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[[Image:Vs100-memory-map.png]]
 
[[Image:Vs100-memory-map.png]]
 +
 +
==RAM memory map==
 +
 +
Most of the RAM is available for uploaded software.  However, regions at the ends are used by the ROM for fixed purposes:
 +
 +
{| class="wikitable
 +
|-
 +
| 000000
 +
| 32 longwords
 +
| Exception vectors
 +
|-
 +
| 000080
 +
| 15 longwords
 +
| Saved screen contents under mouse pointer
 +
|-
 +
| 0000C0
 +
| two words
 +
| Mouse x,y copied from hardware register
 +
|-
 +
| 0000C4
 +
| two words
 +
| Old mouse x,y screen coordinates
 +
|-
 +
| 0000C8
 +
| two words
 +
| New mouse x,y screen coordinates
 +
|-
 +
| <01FFC0
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| extends towards lower addresses
 +
| Stack
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|-
 +
| 01FFC0
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| one longword
 +
| Keyboard fifo read pointer
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|-
 +
| 01FFC4
 +
| one longword
 +
| Keyboard fifo write pointer
 +
|-
 +
| 01FFC8
 +
| one longword
 +
| Tablet fifo read pointer
 +
|-
 +
| 01FFCC
 +
| one longword
 +
| Tablet fifo write pointer
 +
|-
 +
| 01FFD6
 +
| 16 bytes
 +
| Keyboard output fifo
 +
|-
 +
| 01FFE6
 +
| 16 bytes
 +
| Tablet output fifo
 +
|-
 +
| 01FFF6
 +
| one byte
 +
| Size data in keyboard fifo
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|-
 +
| 01FFF7
 +
| one byte
 +
| Size data in tablet fifo
 +
|-
 +
| 01FFF8
 +
| one byte
 +
| Mouse buttons
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|-
 +
| 01FFF9
 +
| one byte
 +
| Keyboard input (LK201 code)
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|-
 +
| 01FFFA
 +
| one byte
 +
| Tablet input
 +
|-
 +
| 01FFFB
 +
| one byte
 +
| State of CTRL and SHIFT, for entering maintenance menu
 +
|}
  
 
==Error LEDs==
 
==Error LEDs==

Revision as of 19:45, 18 February 2023

Some random notes from running the DEC-supplied standard firmware for the VAXstation 100 in an emulator.

The firmware analyzed announces itself as version 05.00. It deviates in minor details from the information in the 1983 "VS100 Engineering Specification".

Memory map

Firmware 5.00 extends the LOOPBACK region to one more word at 4A0004. Apparently this loops back the value written to 480004.

The BBA scratchpad has been moved to 30000. An accesses to a byte at 280000 seems to clear a BBA interrupt.

Vs100-memory-map.png

RAM memory map

Most of the RAM is available for uploaded software. However, regions at the ends are used by the ROM for fixed purposes:

000000 32 longwords Exception vectors
000080 15 longwords Saved screen contents under mouse pointer
0000C0 two words Mouse x,y copied from hardware register
0000C4 two words Old mouse x,y screen coordinates
0000C8 two words New mouse x,y screen coordinates
<01FFC0 extends towards lower addresses Stack
01FFC0 one longword Keyboard fifo read pointer
01FFC4 one longword Keyboard fifo write pointer
01FFC8 one longword Tablet fifo read pointer
01FFCC one longword Tablet fifo write pointer
01FFD6 16 bytes Keyboard output fifo
01FFE6 16 bytes Tablet output fifo
01FFF6 one byte Size data in keyboard fifo
01FFF7 one byte Size data in tablet fifo
01FFF8 one byte Mouse buttons
01FFF9 one byte Keyboard input (LK201 code)
01FFFA one byte Tablet input
01FFFB one byte State of CTRL and SHIFT, for entering maintenance menu

Error LEDs

Indicates which test failed. During power-up, green light turned off. During idle loop, green light remains on.

Vs100-diagnostic-led-errors.png

Apparently there's a bug.

VS100-TT-7.png

Interrupts

All VS100 interrupts use the autovector feature.

Firmware 5.00 doesn't use the level 1 interrupt. The firmware only reads the mouse position during maintenance test.

VS100-interrupts.png

Keyboard test

The firmware transmits code FD (hex) to the LK201 keyboard, which commands it to jump to the power-up sequence and self-test. The keyboard transmits a four-byte message back. The VS100 ignores the keyboard ID, and checks that the third is not 3D.

This information is from the VT220 Technical Manual.
LK201-powerup.png

D0 flags

The firmware maintains a set of flags in register D0.

Bit (decimal) Meaning
16 Manufacturing mode.
17 BBA present.
18 Link down.
19 Power-up error.
20 LEDs locked.
21 Suppress printing test result.
22 In maintenance menu.
23 Keyboard ok.
24 BBA done.
25 Vertical retrace interrupt.
26 Test not executed. (E.g. hardware not present.)
27 Test timed out.
28 Host wants attention. (Same vector as TRAP #1?!?)

Built-in graphics

The firmware has a mouse pointer, a text font, and three icons. The first two are straight bitmaps, whereas the icons are run length encoded.

This icon is displayed when a user can be logged into the system.
VS100-Login.png

This icon is displayed when there's an internal error.
VS100-Trouble.png

This icon is displayed when there's a communication problem.
VS100-Unable.png

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