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Support for VT100 dot stretching

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This commit is contained in:
Jeff Parsons 2016-08-08 11:19:06 -07:00
commit f7464dd182
7 changed files with 4890 additions and 4701 deletions
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89
modules/pc8080/lib/chipset.js
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@ -100,6 +100,12 @@ function ChipSet(parmsChipSet)
Component.subclass(ChipSet);
/*
* NOTE: The STATUS1 port could have been handled entirely by the Keyboard component, but it was just as easy
* to create a simple ChipSet interface, updateStatus1(), that the Keyboard calls whenever it wants to simulate a
* button press or release. It's a six-of-one, half-a-dozen-of-another choice, since technically, Space Invaders
* doesn't have a keyboard.
*/
ChipSet.SI1978 = {
MODEL: 1978.1,
STATUS0: { // NOTE: STATUS0 not used by the SI1978 ROMs; refer to STATUS1 instead
@ -168,8 +174,33 @@ ChipSet.SI1978 = {
*
* <cpu id="cpu8080" model="8080" cycles="2764800"/>
*
* where 2764800 = 24883200 / 9. Beyond that, we don't really care about that particular 8224. I only mention it
* because knowing the CPU frequency is helpful for simulating some of the other circuits below that we DO care about.
* where 2764800 = 24883200 / 9. You need to know this because we rely on the CPU frequency for simulating some
* of the other VT100 circuits.
*
* For reference, here is a list of all the VT100 I/O ports, from /devices/pc8080/machine/vt100/debugger/README.md,
* which in turn comes from p. 4-17 of the VT100 Technical Manual (July 1982):
*
* READ OR WRITE
* 00H PUSART data bus
* 01H PUSART command port
*
* WRITE ONLY (Decoded with I/O WR L)
* 02H Baud rate generator
* 42H Brightness D/A latch
* 62H NVR latch
* 82H Keyboard UART data input [used to update the Keyboard Status Byte -JP]
* A2H Video processor DC012
* C2H Video processor DC011
* E2H Graphics port
*
* READ ONLY (Decoded with I/O RD L)
* 22H Modem buffer
* 42H Flags buffer
* 82H Keyboard UART data output
*
* Most of these are handled by the ChipSet component, since it exists as sort of a "catch-all" component,
* but some are more appropriately handled by other components; eg, port 0x82 is handled by the Keyboard component,
* so it's defined there instead of here.
*/
ChipSet.VT100 = {
MODEL: 100.0,
@ -202,13 +233,65 @@ ChipSet.VT100 = {
STANDBY: 0x7
},
WORDMASK: 0x3fff // NVR words are 14-bit
/*
* The Technical Manual, p. 4-18, also notes that "Early VT100s can disable the receiver interrupt by
* programming D4 in the NVR latch. However, this is never used by the VT100."
*/
},
/*
* DC012 is referred to as a Control Chip.
*
* As p. 4-67 (117) of the VT100 Technical Manual (July 1982) explains:
*
* The DCO12 performs three main functions.
*
* 1. Scan count generation. This involves two counters, a multiplexer to switch between the counters,
* double-height logic, scroll and line attribute latches, and various logic controlling switching between
* the two counters. This is the biggest part of the chip. It includes all scrolling, double-height logic,
* and feeds into the underline and hold request circuits.
*
* 2. Generation of HOLD REQUEST. This uses information from the scan counters and the scrolling logic to
* decide when to generate HOLD REQUEST.
*
* 3. Video modifications: dot stretching, blanking, addition of attributes to video outputs, and multiple
* intensity levels.
*
* The input decoder accepts a 4-bit command from the microprocessor when VID WR 2 L is asserted. Table 4-6-2
* lists the commands.
*
* D3 D2 D1 D0 Function
* -- -- -- -- --------
* 0 0 0 0 Load low order scroll latch = 00
* 0 0 0 1 Load low order scroll latch = 01
* 0 0 1 0 Load low order scroll latch = 10
* 0 0 1 1 Load low order scroll latch = 11
*
* 0 1 0 0 Load high order scroll latch = 00
* 0 1 0 1 Load high order scroll latch = 01
* 0 1 1 0 Load high order scroll latch = 10
* 0 1 1 1 Load high order scroll latch = 11 (not used)
*
* 1 0 0 0 Toggle blink flip-flop
* 1 0 0 1 Clear vertical frequency interrupt
*
* 1 0 1 0 Set reverse field on
* 1 0 1 1 Set reverse field off
*
* 1 1 0 0 Set basic attribute to underline*
* 1 1 0 1 Set basic attribute to reverse video*
* 1 1 1 0 Reserved for future specification*
* 1 1 1 1 Reserved for future specification*
*
* *These functions also clear blink flip-flop.
*/
DC012: { // generates scan counts for the Video Processor
PORT: 0xA2, // write-only
INIT: 0x00 // for lack of a better guess
},
/*
* As p. 4-55 (105) of the July 1982 Technical Manual explains:
* DC011 is referred to as a Timing Chip.
*
* As p. 4-55 (105) of the VT100 Technical Manual (July 1982) explains:
*
* The DCO11 is a custom designed bipolar circuit that provides most of the timing signals required by the
* video processor. Internal counters divide the output of a 24.0734 MHz oscillator (located elsewhere on the