The Advanced User Guide for the Acorn Electron
Cassette motor control, bit 6
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- CAPS LOCK LED control, bit 7
Cassette motor control, bit 6Setting this bit to ‘1’ will turn the cassette motor on. Setting it to ‘0’ will turn the motor off. Motor control is effected by a small relay contact inside the Electron. It is possible to use this to switch small battery operated equipment on and off (for example a transistor radio). CAPS LOCK LED control, bit 7Setting this bit to a ‘1’ turns on the CAPS LOCK LED on the side of the keyboard. A ‘0’ turns it off again. SHEILA &FE08 to &FE0F - the colour palette These addresses in the ULA define the mapping between the logical colours which are provided by programs and the physical colours which are displayed on the screen. For example, in the two colour mode, logical colour 1 will actually produce a colour defined by &FE08 bit 6 (blue), &FE08 bit 2 (green) and &FE09 bit 2 (red). The bits are negative logic, which means that a ‘1’ in bit 6 of &FE08 will ensure that blue is turned off for colour 1. The cursor and flashing colours are entirely generated in software: This means that all of the logical to physical colour map must be changed to cause colours to flash.
Figure 14.7a – 2 colour mode palette
Figure 14.7b - 4 colour mode palette
Figure 14.7c - 16 colour mode palette 14.2 The keyboard The keyboard is mapped to ROM numbers 8 or 9, and may be read directly by accessing memory locations within either ROM corresponding to particular keys. This is useful as a technique for speeding up the machine, as it allows normal keyboard scanning by the OS to be disabled using OSBYTE &B2 (178). See section 15.4 on how to select paged ROMs. The following table lists the relevant memory locations and the bits within each location which represent the keys.
NC=No Connection 15 Outside the Electron 15.1 Introduction to expanding the Electron This chapter is intended for those who want to add their own bits of hardware onto the Electron. There are several reasons for doing this. The most common one is to allow the Electron to access facilities provided for the BBC Micro. All of the common interfaces such as discs, printer port, analogue to digital converter, speech chip, paged ROMs etc. can easily be added onto the Electron. If care is taken with the design, these products will operate in an almost identical manner to those on the BBC Micro. Several interface add-ons can already be purchased from Acorn. If the only point in adding hardware onto the Electron were to make it totally BBC Micro compatible, there would have been little point in buying the Electron in the first place. In fact, the Electron has more potential for expansion than a BBC Micro. Why? Because all necessary system buses come out on the expansion connector. This ability to access all of the buses means that the devices which can be added onto the Electron are limited only by the imagination (and maximum allowable loading of the buses). Appendix G provides a summary of the expansion devices available for the Electron, grouped by generic type. 15.2 The Expansion Connector All required signals from the Electron are present on this connector. In order to make use of them, a basic knowledge of interfacing to the 6502 will be required. Such a knowledge can be acquired by reading some of the popular electronics magazines and specialised books on interfacing. The aim in this book is to explain all of the details to those who have already read enough about microcomputer hardware in general, and now want to know about the Electron in particular.
Figure 15.1 - Expansion connector layout Directory: mirrors -> www.bbcdocs.com -> filebase mirrors -> Soundtracker 6 User Manual Last changes to Soundtracker done on : see program. Soundtracker-Update done by : MnemoTroN mirrors -> Add: Add the function to select the frequency for ntsc / pal in "System Setup" of "Display Setup". mirrors -> Phone Monitoring User Manual mirrors -> Remote Control Center Professional version user manual for Android index mirrors -> 1. Package Contents mirrors -> All About [inline] Apple [inline] iigs basic page content composed, converted, compiled, edited and copyright (c) 1997 by Charles T mirrors -> Transacciones Reportables mirrors -> Device manual of High Speed 4 Port Web Server filebase -> Toolkit plus Download 1.6 Mb. Share with your friends:
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