Sinclair ZX Spectrum Service Manual
Spectrum For Everyone https://spectrumforeveryone.com/
14
Figure 1.4. Keyboard Lower Membrane
The row signal(s) is subsequently buffered by the ULA and placed on one of the five low order data bus
lines. For example, if the CAPS SHIFT key is pressed, row one output drives data bus D0 high, and so on.
The sequence ends with I/O address 7F when column 8 is addressed. In this instance, operation of the
SPACE key drives D0 high. Clearly, the keyboard scanning routines make the distinction between the
CAPS SHIFT and SPACE key by knowing which address line is being driven.
If one of the following keys is pressed the corresponding switch contact on the lower membrane is
closed. Additionally, the CAPS SHIFT switch contact on the upper membrane closes.
TRUE VIDEO EXTEND MODE CURSOR RIGHT
INV VIDEO EDIT CURSOR LEFT
BREAK CAPS LOCK CURSOR UP
DELETE CURSOR DOWN
GRAPH
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