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When the "plot" bit (bit 7) of the attribute byte was high, it indicated that as a substitute of producing one of the 128 glyphs, the 8b of the character byte should be displayed as a substitute as a 2x4 grid of fat pixels. A given cell could have chose between either one in all 128 glyphs, or any of the 256 combos of a 2x4 block graphics glyph. With the deluxe keyboard choice, all 256 values may very well be immediately produced by the keyboard. Instead, a small 32 byte PROM, learn in from 8080 input port 0x80 to 0x8F, provided the timing values. Aside from the scroll offset and the cursor addressing registers, the timing was set shortly after the CPU got here out of reset, and the expectation was that it wouldn't be written once more. In 1978, TRS-80s and Apple IIs came commonplace with a cassette, and a floppy was many hundreds of dollars more. The floppy disk system is just slightly more subtle than that used by the 8-track drive.

Most other system have a tiny ROM routine to learn a boot sector from the disk, which then masses in a 2nd level disk working system, allowing for bug fixes and enhancements after the actual fact. Three would hearth, challenge an RST 3 instruction to the 8080. That routine would then drive one row of the keyboard, then learn that parallel port to sense which keys related to that row were depressed. Parallel and serial communications and a handful of programmable timers have been managed by the TMS 5501 I/O chip. The keyboard used by the Compucolor II was connected via a ribbon cable by way of the 5501 parallel port. The predecessor of the Compucolor II was the ISC 8001, which originally used an 8-track drive for storage. When the drive is chosen, the motor spins up the floppy. What refers to the variety of separate staggered power winding's in the motor or alternator? The term you're referring to is "phase." In a motor or alternator, the number of separate staggered energy windings is thought because the phase. If the sensor could possibly be made inexpensively, then the ability of the Internet could possibly be used to gather numerous samples over massive areas.

Once the fitting observe and sector are discovered, the software program switches on the write enable after which writes the information block. The 5501 has a simple RS-232 model serial interface: one start bit, 8 data bits, one stop bit, costing 10 bits per byte. Bits 6:Zero of the byte chosen considered one of 128 glyphs: usually the letters A-Z, the digits 0-9, and the standard ASCII punctuation, but in addition a large number of small icons and shapes that could be pieced collectively. If the disk velocity is off by just a few p.c, especially if the system which wrote the sector was completely different than the system reading it, bits might be dropped or inserted. The reason the reminiscence mapped video handle range is duplicated is to allow a trade-off between speed and high quality. There is no such thing as a purpose why a couple of the I/O port ranges appear twice; it is just incomplete decoding of the port deal with bus, saving a bit of logic. Because there were no diodes to ensure each row could be sensed independently of key depressions on other rows, the keyboard didn't have any rollover capability.

One advantage of this model of scanning is that for sport play, it was attainable to tell when a given key was depressed, held down, or released, not just that it had been pressed. Not solely did this save pricey electronics, the coloration bandwidth was better than NTSC would permit, leading to crisper graphics than would have been doable with modulation. This mode is used solely when the ROM is clearing the screen, where 4 KB bytes must be written as quickly as doable, and slightly tearing shouldn't be a problem because the display goes to be displaying a solid coloration anyway. That was enforced solely by software program convention, and by poking reminiscence one might do bizarre issues like draw the highest half blinking and the underside half not, or the highest half one shade and the underside half one thing else. In the conventional handle range, the place the user is usually simply poking a byte at a time while typing or printing text, stalls the 8080 CPU till the horizontal blanking interval, at which point the video technology would not must access RAM. Because the display RAM is multiplexed between the video generation circuitry and the need for CPU accesses, one thing have to be done when each want to access video reminiscence at the identical time.