Radio Shack TRS-80 Service Manual page 43

THE. ABOVe. KEYS (MODES) ARE CONNECTED
IN "PARALLEL WITH THE SIMILAR f<.EYS OF
THE. KEYBOARD MATRIX.
'R "P 5 : 3250.JL
IB -;>>-__
~~p
_ _
~rI>-D~---:2~~>--
'RE.SET SWITCH
IWt.
»>----
20
'"
DGA
L5
,
..
D4A
13
D3A
12
DZA
"
DIA
- - - - - - - - - - - - -; "PI
CABL£{~~~~~~~!~~~,:J~-_-~-:l-_-_-~:!~~~:r ~ ~--:r------:r~~~~:t--~::
{
""P"
I· - - - -"1 PtO
RP5 :z.
MC/4¢5¢B
t
5
V
_---l.....-.
--t-'O-----~----<l>--___f
KYBD~
74LS24tP
U6&
I
UZl'5
I
A.2.~
~
I
U35
I
A5~
~
I
I
I
THESE "PARTS MOUNTED
ON PROCESSDR BMW
I
UI!>4
I
~ Zllz2
AI
'05
I
I
US4
I
A7~
74LS05 :
FIGURE 5F. MODEL III CPU SCHEMATIC DIAGRAM - KEYBOARD SECTION
36