Radio Shack TRS-80 Service Manual page 6

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2-3. MPU Bl ock diagram
Control signa'
Back plate
(8 bit)
•
"8
u -
• 0
'd
s
c
c
0
.2
u
t;: :::>
·~
=~
.=
Beek
plate
driver
Address conuol
-
~
Input port
"
18 bit>
;
"
lrnorn1I
reol1tt1
.=
2
lnttrnel bus
c
0
u
Date bus
(8 bh)
~
..
/\
L
u
t
t i
F1
Yee GND
Table below shows the internal register.; of the
MPU
that consiu of S·bit x
14 RAM
storages.
"'
PL
Su
SL
!Ill
W t
/\ E
Uu
Ut
Vii_
Yt
Xn Xt
...... Program counrer
...... Stack pointer
...... W
~sister
•••••• A register, E register
...... U
register
...... Y re&iJter
...... X register
} Exclusive registers
} G<_, , . .
~
••""
MPU registers c-0ns. i st of two groups of registers; exclusive register group ilnd general purpose re-g.is1er group.
Exclusive regis t crs cons ist of program counter (PH, PL) ( l 6 bilsl, stock pointer (SH, SL) ( 16 bits] , and W register
(Wtl,
WL)
(16bils] .
General purpos.e regis ters consist of eight 8·hit registers; U register (UH, UL), X register (XH, XL), and Y regis ter (YH, YL) can
be used in pair l o comprise 16·bit registers.
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