Radio Shack TRS-80 PT-210 User manual

CONTENTS
Page
Introduction .......................................................................... 1
Specifications .......................................................................... 2
...............................................................................
General 4
Description
of Function .................................................................. 7
.......................................................................
Modem Interface 12
.....................................................
Description Keyboard Interface Circuit 18
........................................
Power Slupply and Power Supply Protective Circuits 19
................................................
Operational Description of the Control Unit 20
..............................................................
RS-232C Interface (Option) 33
Block Diagram
......................................................................... 36
MaintenanceProcedure
................................................................. 37
................................................................
Disassembly Instructions 38
Components
........................................................................... 38
Disassembly of PT-210 Portable Data Terminal
.............................................39
..................................................
Replacement and Adjustment within PCB 47
................................................................
Description of Assembly 47
Replacement ........................................................................... 47
............................................................................
Adjustment 54
Troubleshooting
........................................................................ 59
....................................................
Problems at Power-ON (Restore) Time 59
..................................................................
Problems in Operation 60
...................................................................
Printed Circuit Boards 64
........................................................................
Wiring Diagram 70
.............................................................................
Parts Lists 71
........................................................................
ExplodedViews 83
....................................................................
Schematic Diagrams 86

Introduction
Model PT-210 is a Portable Data Terminal that combines a thermal printer, a keyboard, and an acoustic
coupler. Electronic circuits are used for its control; its main control comes from a one-chip microcomputer
(hereinafterabbreviated as pCPU).
Separate units are provided for different functions. Pulse motors and solenoid are used as drive sources
for mechanicals. Simplificationis achieved by minimizing the number of mechanical parts, Accordingly, the
number of points which require adjustment is extremely small and maintenance is easy.
Other units also incorporate electronics. Electronic circuits are simplified for improving reliability and
stability, and the number of parts is minimized.

I / Specification
Data Transmission
.......................
Communication method Start-Stop Asynchronous
.........................
Communicationspeed 110/300bps; Switch selectable
110bps (11bit/character)
300 bps
d Obitlcharacter)
.........................
Communication mode Half/Fullduplex; Switch selectable
ASCII for Information Interchange
...................................
Line status On line/Off line; Switch selectable
................................
Line buffer.. .48characters; On received
....................................
Interface. Acoustic coupling
RS232C (Optional) (CAT. No. 76-1002)
.......................................
Parity. Odd., Even, Ignore; User selectable
....................................
Keyboard Matrix full keyboard
99 codes generated
67 printablecharacters
32 control characters
Printer
.....................................
Method. Non-impact, thermal-paper printing
..................................
Head life.. .20million word
......................................
Paper. .8-
1 /2" (1 00 ft) (CAT. No. 76-1003)
.............................
Character size.. .2.7 mm
X 2.0 mm (7 X 5 dot-matrix)
................................
Line length.. .8inches
10character per inch
80character per line
...............................
Line spacing.. .6lines per inch
Printing rate 50 characters per second; except CR time
.......................................
CR/LF Automatic at column 81
; no code is transmitted
....................................
CR time .0.80 seconds (OFF LINE)
0.86 seconds <ONLINE)
...................................
LF time.. .0.05 seconds (single step)
0.03 seconds (continuous step)
Acoustic Coupler
.................................
Compatibility Bell System 103A (equivalent)
Telephone (CAT No. 43-301)
.......................................
Mode. Oriainate
..................................
Modulation. Frequency shift keying (FSK)
..........................
Receive Frequencies. Originate
Mark 2225
Hz
Space 2025 Hz
.......................
Transmitter Frequencies. Originate
Mark 1270Hz
Space 1070Hz

Receive Sensitivity ............................ - 35 dBm
Transmit Power.
.............................. - 15 dBm
Â
(within 15 dBm difference between transmit level and
receive level)
I
Physical
Size (overall) ................................. 15.7" X
14.6" X 4.9"
(40.0 cm
X 37.2 cm X 12.5 cm)
Weight (Overall)
.............................. 15.0 pounds (6.8 kg)
Power Requirements
Voltage. ..................................... 105 through 1 35 volts
Frequency..
................................. .47 through 63 Hz
Power (Overall)
............................... 75 watts maximum
Environment
Temperature ................................. Operating 50° to 95OF (10° to 35OC)
Storage 40° to 104OF (-4O0C to 71OC)
(not including paper)
40° to 1OZ° (-40"C to 40°C
(including paper)
Humidity.
.................................... Operating 10%to 80% (no condensation)
Storage 10%to 90% (no condensation)

Duplex
Line
Duplex
(OptionalCat. No.
76-1002)
LOca' 1 Remarks
Network
-A
Electric Typewriter
Modem
Modem
I
Note: d) Keyboard : ASCII ..... 99 codes generated.
@ Printer: Non-impact, thermal-paperprintingfive by seven, 80 characters per line.
@ Acoustic Coupler: Compatibility ..... Bellsystem 103A (orequivalent).
(?) Self Test: Turning Power on while holding REPT key starts self test.
(MODES.W-HALF, SPEED S.W-300)
All printablecharacters are printed. Self test ends byturning power off.

MODEL PT-210 COMMUNICATION DIAGRAM
OFF-LINE
IÑÑÑÑÑÑÑÑÑÃ
I
1
1 KEYBOARD CONTROL PRINTER !
1 use as electric typewriter.
I I
I
I
1
Either Transmit or Receive at one
time
I
' KEYBOARD CONTROL PRINTER 1
I-
COMPUTER
1
I
I
I
I.
1 ACOUSTIC 1
I COUPLER 1 MODEM
1 KEYBOARD CONTROL PRINTER 1
1 Transmit and Receive at same time
I
I I
*
r---
I
'
I
L----
' I
-I--------
I
I
-
Telephone-
-
I
I
I
I
I
- --
COMPUTER
LÑÑÑÑ --- -- -- -- ÑÑ
Line
b
ON-LINE
I
I
I
I
RS-232C INTERFACE (OPTIONAL)
! KEYBOARD CONTROL PRINTER 1
ACOUSTIC 1
COUPLER
I
MODEM
Figure 2.
6
1
_^ 1
I
Telephone-
-
!------- --___ ------ J Line

* Character print
One character is composed of the 7
X 5 matrix dots. Assume letter "H" is to be printed. When Carriage
Return and data
"H" signals reach the printer, the line feed motor runs and the thermal head is caused
to move in the direction indicated in the figure on the left.
When the thermal head moves and the row of dots reaches position A, alt dots (1
- 7) are heated and
(
the color. of the paper is changed. When the thermal head advances to position B, only dot (4) is
heated. Identically, as the thermal head advances and the row of dots reaches positions C,
D, and E,
dots (41, (4) and (1 - 7) are heated, and pattern "H" is printed on the printing paper.
Direction of movement of the thermal head
:>
A = E/print
1 uaam
2IUDOI
31nna1
411111
51nnnm
6innaI
71nou1
Figure 5.
The relationship between thermal head feed and dot printing positions is as shown below. (Since con-
trol signals are controlled by the pCPU,
it is not possible to make adjustment.)
1 Character
Carriage Return
Motor
Thermal Head
Figure 6.
8

Keyboard Unit
Â
When a key that corresponds to the data to be input is pressed, its contact operates and a signal is sent
to the control unit.
Printer Unit
The printer unit is controlled by the control unit.
It prints data to be transmitted and receives data on ther-
mosensitive paper (inroll). In the OFF-LINE mode, the printer can be used as an ordinary typewriter.
CR motor assembly
The
CR motor controls movement of the thermal head.When a control signal is input to the CR motor,
the motion of the motor is transmitted to the head assembly@ fixed by the
CR timing belt (2) through
the motor timing pulley
(l) on the motor shaft.
Assembly
Figure 7.
The motor causes the thermal head (A) to move, in the direction of X-axis, a distance that corresponds
to the size of one character, and to do so within
6 pulses of the motor control signal. Therefore, its
moving distance is
2.54 rnrn (1 /lo'').
The motor reverses when the head has travelled the distance of 203.2 mm, which is the effective
travel of the thermal head good for
80 characters, and the head assembly (3) is caused to return to the
start point. The start point is determined by the photo interrupter assembly
(5) While the thermal head
is returning to the start position,
it is not in contact with the thermosensitive paper because of the op-
eration of a relief solenoid.

@ LF motor assembly
The
LF motor controls the feeding of the thermosensitive paper.
Figure
8.
The motion of the LF motor is transmitted to the motor timing pulley (4) set on the platen shaft (3)
through the motor timing pulley @and the LF timing belt (2) and is further transmitted to the platen
(5) The thermosensitive paper is led in by the friction force of the platen@ and then is fed by the ro-
tation of the platen
(5) as pressure is applied to the paper by pinch rollers.
The
LF motor feeds paper in the direction of Y-axis by a distance of 1 line; that is, it moves 4.23 mm
(1/6") after 6 pulses of the LF motor control signal. The thermal head is not in contact with the ther-
mosensitive paper during line feed, due to the operation of a relief solenoid.
Solenoid assembly
The solenoid assembly controls printing motions by causing the thermal head to make contact with
thermosensitive paper and to make a relief from the paper.
When a control signal
is input to the solenoid, the solenoid is actuated and a rotary motion is trans-
mitted to the head shaft
(3) through the head lever (2) which is coupled with the plunger @ The
underhead
(4) is coupled to the head shaft (3\ and the thermal head assembly @ is set to the under-
head.

Solenoid Assembly 1 ' (2) to^)
Figure 9.
A gap is produced between the thermal head (5) and the paper by the rotary motion of the head shaft
0.
While the solenoid is not actuated, the thermal head is in contact with the thermosensitive paper so
that
a print can be made at any time.
It is possible to adjust the pressure of the thermal head applied to the thermosensitive paper by chang-
ing the tension of the tension spring @located at the end of the
Control Unit
The control unit controls the recording of input/output data, the transformation of signal levels (TTL level
- sound) and the transmission and receiving of data. Refer to the description of circuits and interface for
details.

Modem Interface
This equipment modulates digital signals transmitted from the control side into analog signals, and then
transmits them to the mouth side of the handset.
On the other hand,
it demodulates analog signals received from the ear side of the handset into digital
signals, and then transmits them to the control side.
The configurationcan be divided into
a speaker output unit, a microphone input unit, and a modem board
unit. Coupling transmission/receiving is made with the speaker output unit attached to the transmission
side of the handset and with the microphone input unit mounted to the receiving side of the handset. The
modem board mounts modulation and demodulation circuits.
Figure 10. Configuration

CN2
I
T - ~TXD -
BUFFER - - MODULATOR
-
I
I
CONTROL
UNIT
CN3
Figure 11. Modem Logic Block Diagram
l-
- DSR
Names used in the modem logic are described below.
DSR (Data Set Ready): This signal indicates that the modem is in the status that permits operation in
the case where exchange of data is made between a modem and its control unit. This signal becomes
"L" level about 2- 4 seconds after input of data to MIC IN, and operation is enabled.
RxD (Required Data): Receivesdata signals transmittedfrom the modem and transfers them to the con-
trol side.
TxD (Transmitted Data): Transmits data signals - data signals produced from the control side are
transmitted to the modem.
INH (Inhibit): Signal for discontinuing transmission of data. Transmission is made while this input is at
level
"L".
MIC IN (Microphone Input Data):" The following analog frequencies are received from the telephone
handset.
Mark: 2,225
 5 Hz
Space: 2,025 Â 5 Hz
SP OUT (Speaker Output Data): The following analog frequencies are transmitted to the telephone
handset.
Mark: 1,270
& 5 Hz
Space: 1,070 Â 5 Hz
DEMODULATOR 1 RxD
I
-
I
BANDPASS.
FILTER
i
-

Description of Operation
Modulator
Jl
A*.
I
TxD
-
INH
SP
7405 OUT
Figure 12.
Audible sound data is output to SP OUT, and a digital signal is input to TxD when signal "L" (transmis-
sion enable) is input to
INH.
The timing chart is as follows:
SP OUT
Figure 13.

Demodulator
COMPARETER
RxD 0
Â
+5V-+12V
-
Figure 14.
The analog data signal input through MIC IN is amplified by the amplifier, its noise is cut by the band
pass filter, and it is then input to the demodulator. The demodulator contains
a frequency comparison
circuit, and it outputs the difference in frequency by
a digital signal.

33.3 ms I 33.3 ms
1-1 300 Baud
Mark
. .
RxD., TxD
(Odd., Even Parity)
-START Bit 1 -STOP Bit
- Parity Bit: Odd or Even
Mark
1-2 110Baud
100 mS
Mark
1
DATA Bit (7 Bits)
START Bit Parity Bit: Odd
or Even
,
Mark
RxD., TxD
(Odd, Even Parity)
Space
1 Bit1 DATA Bit
(7 Bits)
11 Bit1 2 Bits
I
I STOP Bit
start Bit NON-Parity Bit
I
1
I
Figure 15. Timing Chart

@ Receiver
ON-LINE
OFF-LINE
-
I
L
CARRIER
(MIC IN)
DSR (OUT)
-
RxD
%
(OUT) 2 *--!--T
Space I
DATA Bit
START Bit
-STOP Bit (1 10 BPS)
@ Transmitter
STOP Bit (1 10, 300 BPS)
Parity Bit
I
ON-LINE
OFF-LINE
= (IN)
-
DSR: Data Set Ready
RxD:
-
Received Data
INH: Inhibit
TxD: Transmitted Data
TxD (IN)
DATA Bit
'cSTART Bit STOPSTOP BitBit
(1(110,10 BPS) 300 BPS)
-parity Bit
/
Figure 16.
-7 -1
! i

Description of Keyboard Interface Circuit
Key Board
LINE FEED
Â¥
1 ESC I -D
BACK SPACE 1 -m
I RETURN I-
PAPER ADV 1-
Key
Matrix
I
SPEED
t
I
SHIFT
1
I CTRL 1-
Control
--
Key
Board
nterface
S379C-5
-
MODE M
Figure 17.