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22 Keyboard
22.1 How does the keyboard work
Fig.22.1. below shows the schematics for the keyboard of R250s.
The function of the keyboard is build of nine signals connected as a matrix with five rows and
four columns.
The rows are called KEYROW 0 – 4 and the columns KEYCOL 0 – 3.
Each crossing between a row and a column can be used as an identification of a key.
A voltage feeds the rows directly from D600 giving the rows a voltage of +3.2 V
When pressing one of the keys of the keyboard turns one of the KEYROW 0 – 4 low.
By doing so the processor knows that a key is pressed and it should start the scanning of the
keyboard to identify which key is being pressed.
If the scanning cannot find an active column it means that the button being pressed is the No
key, ONSRQ ground ONOFF through V701.
4/00021-3/FEA 209 544/18 B
Trouble Shooting Guide, Advanced
Fig. 22.1
.
DC
96(121)
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