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- You can use a colour interrupt to reduce the screen size by blanking out the top 13 or bottom 19 lines . (en)
- If you use the socket in the JAFA Systems RS423 cartridge then you will have a self-contained PRESTEL terminal. (en)
- The other, between &4000 and &6800, is the Mode 4 display area that is actually scanned by the Mode 7 Mk2 circuits. (en)
- Receives text messages from other QWERTYphones, Merlin Tonto and M2105 terminals or any terminal with a V.21 modem (en)
- Now, 640 bits is 80 bytes of information, which means you have to get information out at the rate of 80/40 bytes per microsecond, or 2MHz. (en)
- The processor will run at 1MHz during an access cycle to the RAM. (en)
- Out went the BBC’s 6845 video controller, memory controller, serial IO control and timer chips, all replicated to a greater or lesser extent by the ULA’s all-in-one circuitry. “We could pretty much fit all the functionality of the Beeb [BBC Micro] into a ULA with the exception of the microprocessor and the memory,” says Furber. (en)
- In screen modes 0, 1, 2 and 3 the screen uses all the available memory time slots during the display period. The processor is denied RAM access during 40 microseconds of each 64 microseconds of the 256 lines in 312 which is the display period, and it is made to wait for RAM access until the end of the period. (en)
- The Electron is designed to compete with the Spectrum. The idea is to get the starting price very low, but not preclude expansion in the long term. (en)
- Central to cutting the cost of the new machine was reducing the chip count. In place of the BBC’s various ancillary logic chips, the Electron would employ a single Uncommitted Logic Array chip, a trick Sinclair had employed in the ZX81 and Spectrum; the ZX80 had used off-the-shelf TTL parts. “That allowed us to take a machine which had 102 chips on the motherboard and reduce it to something like 12 or 14 chips,” says Furber, “basically an order of magnitude reduction in the complexity of the motherboard.” (en)
- The processor and the video are competing for access to the RAM, and the RAM can only support a bandwidth of 2 MHz. In screen modes 4, 5 and 6 this is no problem since the screen only needs 1MHz access to the RAM. (en)
- The BBCs Mode 7 uses a teletext display, tt is produced by a special teletext chip which leaves most of the Beeb’s 32K memory free for programs. Graphic displays in Mode 7 are created differently to the displays in the so-called graphic Modes. Teletext graphics characters use a 2x3 grid the same size as an alphanumeric character which gives them a rather chunky look. (en)
- "We had this warehouse in Wellingborough," Hohenberg recalls. "Before Christmas, the trucks were lining up at one end wanting to take the few Electrons we had away to stores, but now the trucks were all at the other end, delivering, and the market had completely dried up. Seeing Electrons piled floor to ceiling... it was very depressing." (en)
- As you can see, in the worst case, the Electron takes 4.3 times as long to run the same program as the BBC micro. (en)
- Take the smaller of the Mode 7 Mk2 boards and lay it on the under side of the Electron board so that the holes in it fit over the pins of the ULA. (en)
- Interestingly, when it came out the Mode 7 Adaptor at £85 cost nearly twice as much as the Electron was going for in many places under the heading of obsolete stock. Because of this at the end of last year John decided to produce a £25 simulator including a Mode 7 screen editor program. (en)
- The processor will run at 2MHz during an access cycle to the ROM. (en)
- To receive TELETEXT you will require a Master RAM board, a User Port and a Morley Teletext Adapter with separate power supply. (en)
- The diagram on page 16 shows 4 pads around IC3 marked R, G, B and Sy. These now need to be wired to the similarly labelled points on page 18. (en)
- you only need a few more bits and bobs to turn the Beeb into a teletext receiver. The Morley Adapter does just that. (en)
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