Tandy PC-6 User manual

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ITANDY®
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POCKET SCIENTIFIC COMPUTER
PC-6
Catalog Number:26-3672
CUSTOM MANUFACTURED FOR RADIO SHACK, A DIVISION OF TANDY CORPORATION

CONTENTS
PAGE
SPECIFICATIONS
•....••..•..•...........•.........•...•....•..•.•........•.•.. 3
How To Open Upper Case ....................................•............••.. 3
THEORY OF OPERATION
...........•......................•.......••.......... 4
Block Diagram
...•..•••..••••...•.•..........•..•.........•.•.....•.....•••. 4
LSI
•............................. · ......................•.......•......... 5
Ram Map ...••.....•••..........•...........•........•.......•............. 5
Buzzer Control Circu
it •..........................................•........... 6
Interrupt Circuit 6
Keyboard
.•.................................................•.........•... 6
Power Supply
........•..................................................... 7
LSI (Pin Functions)
.....•.....•...•............................................. 8
DISPLAY
•..............•..........................................••......... 9
TROUBLESHOOTING GUIDE
.......•........................................... 10
Test Programs
11
Operation Check ........................................•...•.•.•.....•.... 14
PCB ASSEMBLY VIEWS .......••..........•..•.......•........................ 19
PARTS LIST
...........•..•...........................•...................... 20
Electrical
Parts .........•.................•.........•...................... ,20
Mechanical Parts
..................•........................................ 21
EXPLODED VIEW/DISASSEMBLY INSTRUCTIONS 23
SCHEMATIC
DIAGRAM ...•...•...........•.................................... 24
Main Block
..............••........•..•.....•............................. 24
Keyboard
.•....•.••.............••........••..•.......................... 25
Display
.........•.•..••..••.....•.•.......•..••.......................... 26

Display Method
Display
Calculation
Range
Program System
Program
Language
Number of Variables
RAM Capacity
Program
Areas
Number of Stacks
Subroutine
FOR
'V NEXT
LOOP
Operators
Power Supply
Power Consumption
Battery Life
Memory
protection
battery
Auto Power-off
Ambient Temperature
Dimensions
Weight
SPECI FICATIONS
5 x 7 dot-matrix crystal
24-digit, dot-matrix liquid-crystal display
± 10-
99
'V ±9.999999999 x10
99
Stored System
BASIC
26 fixed variables, exclusive character variable
and array variables
7520 bytes (system
area: 672 bytes)
Maximum
of 10 (PO through P9)
8 levels
4 levels
12 levels
2 lithium batteries (CR-2032) for main frame
1
lithium battery (CR-1220) for memory backup
Maximum 0.07W
1) Continuous program execution: approximately 85 hours
2) Continuous display
of 5555555555 at 68° F(20°C): approximately 200
hours
or 5.5 months when unit is used 1hour per day
NOTE: 1hour includes 10 minutes
of condition 1) and 50 minutes of con-
dition 2)
Approximately 2 years (with main batteries installed)
Approximately 6minutes
32° F
to 104°F (O°C to 40°C)
3/4"H x 5-5/8"W x 2-3/4"D (18 mm x142 mm x 71 mm)
5.8 oz (165 g), including batteries
How To Open Upper Case
Tweezers
1. Insert the tweezers into the back of the upper case.
2. Move tweezers gently in the direction indicated by the
arrow in the figure below.
-3-

THEORY OF OPERATION
Block Diagram
KEYBOARD
a1"Va6, d1"Vd6
b1"Vb6, e1 "Ve6
c1 "Vc6, RD"V R14
Km1"VKm12
DOT-MATRIX DISPLAY
5x7dots, 24 digits
a7"Va12, d7"Vd12
b7"Vb12, e7"Ve12
c7"Vc12, RD"VR14
D1-D8,OP, CE, C1, C2
GATE ARRAY
IC4
MB64H193
RAM IC3
HM6264ALFP
OPTIONS
26-3671
26-3651
CMT 26-3652 26-3652
NOTE: Only one of 2options can be connected at a time.
-4-

LSI
Main CPU
HD61747B20
Sub CPU
HD61747B25
Gate Array
MB64H193
RAM
HM6264ALFP-5Q,
BASIC control, Key signal input/output (lower keyboard), 1st to 6th digits and
13th to 18th digits display control.
Calculation, I/O control, key signal input/output (upper keyboard), 7th to
12th digits and 19th to 24th digits display control.
Interface between CPU and RAM, buzzer control.
Stores data and program. RAM has 8K bytes (64K bits) capacity and contains
aself-control circuit.
Ram Map
LSI ROM
RAM
CPU (Main)
HD61747B20 113024 bits 1896 bits
CPU (Sub)
HD61747B25 113024 bits 1896 bits
RAM
~
HM6264ALFP-50 65536 bits
TOTAL
226056 bits 69328 bits
I nput Buffer
Code Buffer
PH
POT
MFT ST
P5T P4T P3T P2T
P9T P8T P7T P6T
OP
RAM
Variable B
P9B
READ#No.
DATA#P
DATA P
P#X
IN-
KEY
IAddress
P#
GOSUB STACK
DISP Buffer
xD
yD
P#
Varia-
ble No
STEP
P# I~aria-
Address
ble No.
000
080
FOR NEXT
-5-
I P# I~aria-)j
ble No
P# l~aria-..1
ble No.
PASS
IIPRT I
DEFM IMODEI
Address kj i
Users Area
Communication Buffer
Variable check I
$
FF I
100
180

Buzzer Control Circuit
There
are 3ways to operate the buzzer:
Key
input, BEEP 0, and BEEP 1
8
Mode
Frequency
Time
BEEPO
0.9 kHz
110
msec.
BEEP 1
4.55 kHz
110
msec.
Key Input
4.55 kHz
11 msec.
A
82 t----=1..-
..,.,....,
81 ----
M864H193
A ---.fLJLJL
8LSlSlJ
Interrupt Circuit
• Interrupt circuit for the clock pulse when VDD2 drops.
1. When the power is on, VDD2 is "L" level.
2.
PG2 through the ICand 26th pin of the CPU receive PG2.
3. When VDD2 drops, the output of the IC becomes "GND" level and the CPU does not receive
PG2.
PG1
HD61747825
f--- PG2
VDD2
• Interrupt circuit for the voltage of the Gate Array and options when VDD2 and SW drop.
1. When the power is on, VDD2 and SW is "L" level.
2.
VDD2 for Gate Array and VDD4 is also "L" level.
3.
When VDD2 drops, VDD2 for Gate Array and VDD4 becomes "GND" level and stops the op-
ration of the RAM and options.
sw~
VDD2(from IC 4) VDD4
VDD2(from IC 2)
Keyboard
HD61747B25 controls the upper keyboard.
Ks2
Ks3'VKs8 Upper
HD6174782 Ks9, Ks10
~
KeYboard
HD61747B20 controls the lower keyboard.
Km1'VKm4
Km5'VKm10 Lower
HD6174782 Keyboard
Km11, Km12
-6-

Power Supply
VSSl
VRAM
VlrvV5
VDDl
VDD2
Power supply voltage for TC4071 BF.
Memory
used to keep the voltage for the RAM.
LCD drive voltages. Voltage
is generated by connecting the external resistor to VDD2.
Power supply for the CPU, RAM and options.
Stays
VDDl at power-on. Goes to GND at power-off or APO (auto power-off).
-7-

LSI (Pin Functions)
IC1 IHD61747B20
IC2,HD61747B25
Pin No. Signal Name
In/Out Function
1'\,,4
D1,2,4,8
In/Out Data in/out (D1, D2, D3, D4)
5INT
In Interrupt signal from RAM
6'\,,18 KM'\"K1
In/Out
Key signal for keyboard
19
SW
In/Out Switch signal. GND at switch
"OFF" and VDD1 at switch
"ON".
20'\,,24 V5'\"V1
Out Display voltage. Divided vol-
tage from VDD1.
25,26 PG2,PG1 Out, In CPU internal clock
27'\,,72 R15'\"R7
Out Display signal
73 GND In GND
74 CE2
In/Out
Chip designating signal.
Select RAM
or other devices
75 CE1
In/Out Select RAM or other devices
76
VDD1 In Power source
77 VDD2 Out VDD1 output from the LSI.
VDD1
at switch "ON" and
GND switch
"OFF".
78, 79 1/)1,1/)2
In/Out Clock pulse
80
OP
In/Out Operation signal
~ ~:e: 80w ~ ~ b: ~ 0: ~ ii ~ ~ ~
o0 U U<:J a1
> > b1
c1
d1
e1
a2
b2
c2
d2
e2
a3
b3
c3
d3
e3
a4
b4
c4
N ..... LO O ..... NM<::t
~~a:~~ o:o:o:a:a:~~<g:g~~
01
02
04
08
INT
KM
K12
K11
K10
Kg
K8
K7
K6
K5
K4
K3
K2
K1
SW
V5
V4
V3
V2
V1
IC4,MB64H193
37
36
100
02
106
03
ADO
04
107
E
AD1
S1
VSS
VSS
AD2
S2
AD10
B2
AD3
B1
DE
CSO
AD4
CS1
AD11
CS2
LD
coco
N0
(J)
r-- 0
co
en
""
M
12
00
00
0 0 s
(fJ (fJ (fJ (fJ
« « ««
««>a: UUU U 25
13
24
Pin No. Signal Name In/Out
Function
1,2
100,106 In/Out
Data in/out
3
ADO
Out
Address signal
4107
In/Out
Data in/out
5
ADl
Out
Address signal
6V55 In Power source
7,8,9 AD2, 10,3
Out
Address signal
10
OE
Out Output
enable
11'V18 AD4'VAD12
In/Out
Address signal
19
VDD In GND
20
RW
Out Read/write signal
22'V24
CS6'VCS3 Out
Ch ip enable signal
25'V27 C52'VC50 -
NC
28,29
Bl, B2 Out Buzzer signal
30 52 In GND
31 V55 In V55
32
51
In GND
33 E-
NC
34'V37
D4'VDl
In/Out
Data in/out
38
OP
In Operation signal
39,40
C2,Cl
In Clock pulse
41 VDD2 In Power
sou rce
42
CE
In Chip enable
43
VDD
In GND
44'V48 103'V105
In/Out Data in/out
-8-

IC3, HM6264ALFB-50
GND 14
Pin No. Signal Name
In/Out
Function
1 NC
-
NC
2'V10 A12'VAO In Address signal
11'V13 1/01'V1/03
In/Out
Data signal
14 GND In VSS terminal
15'V19
1/04'V1/08
In/Out Data signal
20 CE1 In Chip enable
21
A10
In/Out
Address signal
22 OE Out
Output enable
23'V25 A11,9,8
In/Out
Address signal
26 CE2
In
GND
27
RIW
In Read/write signal
28
VDD In GND
DISPLAY
Numbers and characters are displayed
in 5 x 7 dots.
Following
is an explanation of adot-matrix LCD.
e12 c12 a12 e1 c1 a1
60606 60606
00000 00000
00000 Lower electrode 00000
00000-----------00000
00000 00000
00000 00000
09
090
09
090
d12 b12 d1 b1
R8-o0000 00000
R9--D0000 00000
RIO -00000 Upper electrode 00000
Rl1--Q0000--- ----00000
R12-o0000 00000
R13 -aoooa 00000
1"14 -00000 00000
"----------"Vr---------
Left-half 12 digits
e12 c12 a12 e1 c1 a1
~O~O~ do~o~
00000 00000
00000 Lower electrode 00000
00000--- ----00000
00000 00000
00000 00000
O?O?O 090?0
d12 b12 d1 b1
00000 OOOOo-RO
00000 OOOOD--RI
00000 Upper electrode 0000D-R2
00000--- ---OoOOcr-R3
00000 0000~R4
00000 OOOOo--RS
00000 0000CJ-R6
"-------- __ "V_-------~
Right-half 12 digits
e1 d1 c1 b1 a1
+++-t+-I-+++-++-+ __ -R0
--+++++++++-If+t-I+t--R1
--+++-++++++-1++-+++-R2
--+++-+++t+t-tt++H- R3
--+++-+++-I+t-t+++H-RL.
-+++-+f++f++t+-t++-- RS
-++++H-++-H+t-H+-- R6
On the upper electrode of the LCD, common signals RD'V R6 and R8'V R14
are applied horizontally while
other signals al'Vel to a12'Ve12 are applied
vertically
on the lower electrodes as shown in above figures.
In the left figure, the upper-right corner of the dot is displayed when avol-
tage difference exists between signals
RD and al. The CPU outputs the dis-
play signals
to the LCD display.
CPU HD61747B2D controls the 1st to 6th and 13th to 18th digits of dis-
play, while HD61747B25 controls
the 7th to 12th and 19th to 24th digits.
-9-
-----~-----------------------------------------

TROUBLESHOOTING GUIDE
Symptom Cause Solution
No display at all. Weak batteris Replace the batteries.
Poor battery
contact Clean the battery and contact spring.
Lift the battery spring.
Peeled heat seal Replace the heat seal.
Broken heat seal Replace
the heat seal.
LCD (CA51-TS) Replace the
LCD.
LSI (HD61747B) Replace
the LSI.
Acertain segment(s) Peeled heat seal Replace the heat seal.
cannot be displayed. Broken heat seal Replace
the heat seal.
LCD (CA51-TS) Replace
the LCD.
LSI (HD61747B) Replace
the LSI.
Calculation impossible.
LSI (HD61747B) Replace
the LSI.
Acertain
button does not
Poor key contact
Celan the contact pad on the PCB and the
function. key
contact rubber.
Broken
PC line Connect the
PC line.
Peeled heat seal Replace
the heat seal.
LSI (HD61747B) Replace
the LSI.
-10-
-----------~-- -----------