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The 8080 CPU goes through the Bus interfaces for all memory accesses now. The PCjs CPU maintained its own copy of Bus memory structures and interfaces, partly for improved performance but also because some CPUs can turn on address translation (ie, paging), making separate interfaces a necessity. However, PC8080 has much lower performance requirements and no address translation requirements, so we should revert to the original Bus interfaces.

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Jeff Parsons 2016-05-02 12:54:55 -07:00
commit a56f1cfde1
6 changed files with 376 additions and 434 deletions
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14
modules/pc8080/lib/video.js
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@ -56,14 +56,24 @@ if (NODE) {
* bufferCols: the width of a single frame buffer row, in pixels (eg, 256)
* bufferRows: the number of frame buffer rows (eg, 224)
* bufferBits: the number of bits per pixel (default is 1 if omitted)
* interruptRate: normally the same as (or some multiple of) the refreshRate (eg, 120)
* refreshRate: how many times updateScreen() should be called per second (eg, 60)
* interruptRate: normally the same as (or some multiple of) refreshRate (eg, 120)
* refreshRate: how many times updateScreen() should be performed per second (eg, 60)
*
* We record all the above values now, but we defer creation of the frame buffer until our initBus()
* handler is called. At that point, we will also compute the extent of the frame buffer, determine the
* appropriate "cell" size (ie, the number of pixels that updateScreen() will fetch and process at once),
* and allocate our cell cache.
*
* Why interruptRate in addition to refreshRate? A higher interrupt rate is required for Space Invaders,
* because even though the CRT refreshes at 60Hz, the CRT controller interrupts the CPU *twice* per
* refresh (once after the top half of the screen has been redrawn, and again after the bottom half has
* been redrawn), so we need an interrupt rate of 120Hz. We pass the higher rate on to the CPU, so that
* it will call updateScreen() more frequently, but we limit our screen updates to every *other* call.
*
* TODO: Consider alternatives to screenRotation; it's expedient, but I'm not sure how efficient it is,
* and it might be nice (especially for debugging) if we created our own rotated image buffer which we could
* then blast directly to the screen canvas.
*
* @constructor
* @extends Component
* @param {Object} parmsVideo