Radio Shack Tandy 200, 26-3861 Technical Reference Manual

Tandy

200 Technical

Reference

Manual

26-3861

TERMS

AND CONDITIONS

OF SALE AND LICENSE

OF TANDY

COMPUTER EQUIPMENT

AND

SOFTWARE

PURCHASED FROM RADIO

SHACK

COMPANY-OWNED

COMPUTER CENTERS, RETAIL

STORES

AND RADIO SHACK

FRANCHISEES OR

DEALERS AT

THEIR AUTHORIZED

LOCATIONS

LIMITED

WARRANTY

I. CUSTOMER

OBLIGATIONS

„ ,„ j

A. CUSTOMER

assumes

full responsibility that

this computer

hardware purchased

(the "Equipment'

),

and

any

copies of software

included with the

Equipment or licensed

separately

(the "Software") meets the

specifications,

capacity,

capabilities, versatility, and

other requirements

of CUSTOMER.

B. CUSTOMER assumes

full

responsibility for the condition

and effectiveness

of the operating

environment in which

the Equipment and

Software are to

function, and for its

installation.

II.

LIMITED WARRANTIES

AND CONDITIONS

OF SALE

A. Foraperiod

of ninety

(90)

calendar days from the

date of the

Radio Shack sales

document received upon

purchase of the

Equipment.

RADIO SHACK

warrants to the

original CUSTOMER that

the Equipment and the

medium upon

which the

Software is stored is free

from

manufacturing defects. This

warranty It only applicable

to purchases

ol Tandy

Equipment by tha

original

customer from Radio Shack

company-owned

computer

centers, retail

stores, and Radio

Shack franchisees

and dealers at

their authorized locations

The warranty is

void if the

Equipment's case or

cabinet has been opened,

or if the

Equipment or Software

has been subjected to

improper or

abnormal use. If

a

manufacturing defect is

discovered dunng

the stated warranty period,

the defective

Equipment must be

returned to a

Radio Shack Computer

Center, a

Radio Shack retail store, a

participating Radio

Shack franchisee

or a

participating Radio Shack

dealer for repair,

along with a copy of

the sales document or

lease

agreement. The

original CUSTOMER'S

sole and

exclusive remedy in the

event of

a

defect is

limited

to

the

correction

of the defect by

repair, replacement,

or refund of the

purchase price,

at RADIO SHACK'S election and

sole expense.

RADIO

SHACK has no

obligation

to

replace or

repair expendable items.

B. RADIO

SHACK makes no

warranty as to the

design,

capability, capacity, or

suitability for use of the

Software,

except as

provided in this

paragraph. Software is

licensed on an AS

IS" basis, without

warranty. The original

CUSTOMER'S

exclusive remedy,

in the event of a

Software

manufacturing defect, is

its repair or replacement

within thirty

(30)

calendar days of the

date of the Radio

Shack sales

document received upon

license of the

Software. The

defective Software

shall

be

returned to a

Radio Shack

Computer Center, a Radio

Shack retail store,

a

participating

Radio Shack

franchisee or Radio

Shack dealer along

with the sales document.

C. Except as

provided herein no

employee,

agent, franchisee,

dealer or other

person is authorized to give

any

warranties of any

nature on

behalf of RADIO SHACK.

.„

D. EXCEPT AS

PROVIDED HEREIN,

RADIO

SHACK MAKES NO

EXPRESS WARRANTIES,

AND ANY IMPLIED

WARRANTY OF

MERCHANTABILITY

OR FITNESS FOR A

PARTICULAR

PURPOSE IS LIMITED IN

ITS DURATION

TO THE

DURATION OF

THE WRITTEN

LIMITED WARRANTIES SET

FORTH

HEREIN.

E. Some

states do not

allow limitations

on how long an

implied warranty

lasts,

so

the above

limitation(s) may not

apply to

CUSTOMER.

A. EXCEPT AS PROVIDED

HEREIN,

RADIO SHACK SHALL

HAVE NO

LIABILITY OR

RESPONSIBILITY TO CUSTOMER

OR ANY

OTHER PERSON OR

ENTITY WITH

RESPECT TO ANY

LIABILITY, LOSS OR

DAMAGE CAUSED

OR

ALLEGED TO BE

CAUSED

DIRECTLY OR

INDIRECTLY BY

"EQUIPMENT' OR

"SOFTWARE" SOLD. LEASED.

LICENSED

OR FURNISHED BY

RADIO SHACK.

INCLUDING. BUT

NOT LIMITED TO,

ANY

INTERRUPTION OF

SERVICE. LOSS OF

BUSINESS OR

ANTICIPATORY PROFITS OR

CONSEQUENTIAL

OAMAGES

RESULTING FROM

THE USE

OR OPERATION

OF THE

"EQUIPMENT" OR "SOFTWARE."

IN NO

EVENT SHALL RADIO

SHACK

BE

LIABLE

FOR LOSS OF

PROFITS. OR

ANY INDIRECT. SPECIAL.

OR

CONSEQUENTIAL DAMAGES

ARISING OUT OF

ANY

BREACH OF THIS

WARRANTY OR

IN ANY MANNER

ARISING OUT OF OR

CONNECTED WITH THE SALE.

LEASE,

LICENSE, USE

OR ANTICIPATED USE

OF THE

"EQUIPMENT' OR "SOFTWARE."

_

NOTWITHSTANDING

THE ABOVE

LIMITATIONS AND

WARRANTIES. RADIO

SHACK'S LIABILITY

HEREUNOER FOR

DAMAGES INCURRED

BY CUSTOMER OR

OTHERS SHALL NOT

EXCEED THE

AMOUNT PAID BY

CUSTOMER FOR

THE

PARTICULAR

"EQUIPMENT" OR

"SOFTWARE" INVOLVED.

B. RADIO SHACK

shall not be liable

for any damages caused by

delay in

delivering or furnishing

Equipment and/or

Software.

C.

No action

arising out of any

claimed breach of this

Warranty or

transactions under this

Warranty may be brought

more than two

(2)

years after the cause

of action has

accrued or more

than four

(4)

years

after the date of the

Radio

Shack sales

document for the Equipment or

Software, whichever

first occurs.

D. Some

states do

not allow the

limitation or exclusion of

incidental or

consequential damages, so

the above

limitation(s) or

exclusion(s) may not

apply to CUSTOMER.

IV. SOFTWARE

LICENSE

RADIO SHACK grants to

CUSTOMER a

non-exclusive, paid-up

license to use the

TANDY Software on one

computer,

subject to the following

provisions:

A. Except as

otherwise provided

in this Software License,

applicable

copyright laws shall apply to

the Software.

B. Title to the

medium on which the

Software is recorded

(cassette and/or

diskette) or stored (ROM) is

transferred to

CUSTOMER,

but not title to the

Software.

C.

CUSTOMER may use Software

on

a

multiuser or

network system only if

either, the

Software

is

expressly labeled

to be

for use on a

multiuser or network system,

or one copy

of this software is

purchased for each node or

terminal on which

Software is to be used

simultaneously.

D.

CUSTOMER shall not use,

make, manufacture,

or reproduce copies

of Software except

for

use

on one computer

and as

is specifically

provided in this

Software License.

Customer is expressly

prohibited from disassembling

the

Software.

E. CUSTOMER is

permitted to make

additional copies of the

Software only

for backup or archival

purposes or d

additional copies

are required in the

operation of one

computer with the

Software, but only to the

extent the

Software allows a

backup copy to be

made. However,

for TRSDOS

Software, CUSTOMER is permitted

to make

a

limited

number of additional copies

for CUSTOMER'S

own

use.

F.

CUSTOMER may resell or

distribute unmodified

copies of the

Software provided

CUSTOMER has purchased one

copy

of the

Software for each one sold or

distributed. The

provisions of

this Software License

shall also

be

applicable to

third parties

receiving copies of the

Software from

CUSTOMER.

G. All

copyright notices

shall

be

retained on

ail copies of the

Software.

V APPLICABILITY OF

WARRANTY

A. The

terms and

conditions of this

Warranty are applicable as

between RADIO

SHACK and CUSTOMER

to either a

sale of

the Equipment

and/or Software License

to CUSTOMER or

to

a

transaction whereby

Radio Shack

sells or

conveys such

Equipment to a third

party for lease to

CUSTOMER.

B. The

limitations of liability and

Warranty provisions

herein shall inure to

the benefit of RADIO SHACK,

the author,

owner and

or licensor ofthe

Software and any

manufacturer of the

Equipment

sold by

Radio

Shack.

VI. STATE LAW

RIGHTS

„..„

The warranties granted

herein give the

original CUSTOMER

specific legal rights,

and the original

CUSTOMER may

have other rights

which vary from

state to state.

8/85

Chip specifications are reprinted by

permission

of Hitachi

America,

Ltd.,

Semiconductor and I.C. Sales and Service

Division.

Tandy 200

Technical Reference Manual:

°1986,

Tandy Corporation

Reproduction or

use, without express written permission

from Tandy Corporation and/or its licensor,

of

any portion

of

this

manual

is prohibited. While

reasonable efforts

have

been

taken

in the

preparation of this

manual

to

assure its

ac-

curacy,

Tandy Corporation assumes no liability resulting

from any errors or omissions in this

manual,

or

from

the use

of the information contained herein.

Tandy

and Radio Shack are registered trademarks of Tandy

Corporation.

10 987654321

CONTENTS

INTRODUCTION

1-1

External

View

,

1-1

Internal

View

,

1-4

Specifications

1-6

THEORY

OF

OPERATION 2-1

General

2-1

Block

Diagram

,

2-2

CPU

2-4

Memory

2-4

Address

Decoding

and Bank

Selection Circuit

2-7

I/O Map

2-8

Keyboard

2-11

Cassette Interface

Circuit

2-12

Printer

Interface

Circuit

2-13

Bar

Code Reader Interface Circuit

2-14

Buzzer

Control

Circuit 2-15

Clock Control

Cirucit

2-16

Serial

Interface Circuit

2-20

LCD

2-30

Power

Supply

and Auto-Power ON/OFF

Circuit 2-39

APPENDIX

A/ INSTALLATIONS

A-1

Installation

of Operational RAMs

and

ROM

A-1

Installation

of Nickel-Cadmium

Batteries

A-1

APPENDIX

B/ KEYBOARD LAYOUT,

CONNECTOR PIN

ASSIGNMENTS AND

CHARACTER

CODE TABLE .... B-1

Keyboard

Layout

B-1

Connector Pin

Assignments

B-2

Character Code Table

B-7

APPENDIX

C/

TECHNICAL INFORMATION

C-1

80C8SA

C-1

81C55

C-13

82C51

C-19

Basic

Construction

of LCD

C-29

HM6264LFP-12

C-31

HM6264LP-10

C-37

HN613256P

C-45

HN61364P

,

C-49

MC14412

C-51

RP5C01

C-57

APPENDIX D/

200

ROM INFORMATION

D-1

List of

Illustrations

FIGURE

PAGE

NUMBER

DESCRIPTION

NUMBER

1 Front View

1-2

2 Rear View

1-2

3 Bottom

View

1-3

4 Main PCB

1-4

5 LCD PCB

1-5

6 Memory PCB

1-5

7 Organization

2-1

8 Biock Diagram

2-3

9

Functional Block

Diagram of Bus Separation

Circuit

2-4

1 Memory Map

2-5

1

Internal Wiring Diagram of RAM

Package

2-6

12 Bank Selection

Circuit

2-7

13 I/O Address

Decoding

Circuit

2-8

14

I/O Map

and I/O Port Description

2-9

1

Condition of Pressing "T" Key

2-11

16 Write Circuit of Cassette

interface

2-12

17

Read

Circuit

of Cassette

Interface

2-12

18 Remote

Circuit of Cassette Interface

2-13

1

Printer Interface Circuit

2-14

20 Bar Code Reader Interface

Circuit

2-15

21 Buzzer Control

Circuit

2-15

22

RP5C01

Internal Block Diagram

2-16

23

Flowchart for the TIMER IC

2-18

24 Functional Block Diagram

of the Serial

Interface

2-21

25

RS-232C/MODEM Selection

Circuit

2-23

26 RS-232C

Interface Circuit

2-24

27 MODEM IC and Peripheral Circuit

2-25

28 Transmission Filter Circuit

2-26

29 Reception

Filter

Circuit

2-27

30 MODEM Connector Interface

Circuit

2-28

31

Tone

Signal Generator Circuit

2-29

32 Internal Block Diagram

of

HD61830B

2-31

33 Internal

Block

Diagram

of

HD61103

2-33

34

Output

Waveform of HD61103

2-34

35 Internal Block Diagram of HD61100

2-35

36 Output Waveform of HD61100

2-36

37 Driving

Waveform of

LCD

2-38

38

Power Distribution

2-40

39

DC/DC

Converter and Low Power

Detection

Circuit

2-42

40 Power Contra! and Reset

Circuit

2-45

41

Power-Up/Down Sequence

2-46

FIGURE

PAGE

NUMBER

DESCRIPTION

NUMBER

A-1

Memory PCB

A-1

A-2

Installation of

Nickel-Cadmium

Batteries

A-2

B-1

Keyboard

Layout

B-1

B-2

System Bus

Connector

B-3

RS-232C Connector

B-4

B-4 Printer

Connector

B-5

Cassette

Connector

B-5

B-6

Modem Connector

B-5

B-7

Bar

Code Reader

Connector

B-6

C-1 Functional Block

Diagram

C-2

Configuration

of

80C85A

C-3

C-3 Trap

and RESET IN

C-8

C-4 80C85A

Basic

System Timing

C-12

C-5 Functional Block

Diagram

C-1

C-6 Pin

Configuration of

81C55

C-13

C-7

Internal

Register ot

81C55

C-15

C-8 Programming

the Command/Status

Register

C-16

C-9

Reading the

C/S

Register

C-17

C-10 Bit

Assignments to the Timer

Counter

C-18

C-1

Functional

Block Diagram

C-1

C-12 Pin Configuration

of 82C51A

C-20

C-13

Function-Setting

Sequence

C-24

C-14 Bit

Configuration

of

Mode Instruction

(Asynchronous)

C-25

C-15 Bit

Configuration

of Mode Instruction

(Synchronous)

C-26

C-16 Bit Configuration

of Command

C-27

C-17 Bit

Configuration

of

Status Word

C-28

C-18

Construction of LCD Panel

C-29

C-19 Operation Theory

of LCD Panel

C-30

List

of Tables

TABLE

PAGE

NUMBER

DESCRIPTION

NUMBER

1 Port Assignment

of

the 81 C55

2-10

2 RP5C01

I/O Port Address

Assignment 2-17

B-1

System Bus Connector Pin

Assignments

B-2

RS-232C

Connector

Pin Assignments

B-3

Printer

Connector Pin

Assignments

B-4

C-1 Interrupt

Priority,

Restart

Address

and Sensitivity

C-6

C-2

80C85A Machine

Cycle Chart

C-10

C-3

80C85A Machine

State Chart

C-1

C-4

I/O Address

of 81C55

C-15

C-5 Port

Control

Assignment

C-16

C-6 Operation

between

82C51A and

CPU

C-23

in

INTRODUCTION

Tandy 200

portable

computer is an

enhanced version

of

the Radio Shack

Model

100 Portable

Computer. The Tandy

200

is software

compatible with the Mode!

100

in BASIC so that both

system

users can take

advantage of the

large

number of

programs

available.

One

important difference

between

the Model 100

and

Tandy 200 is

the size of

the LCD screen. The

Tandy

200's LCD

screen

is double the

size of

the Model

100's. That is, the

Model

100's display

capability is 40

x

8

characters while the

Tandy 200 has

a display

capability of

40

x

1

6

characters.

The Tandy

200 has

the following

applications programs

in

the

standard ROMs:

BASIC, TEXT,

ADDRSS,

SCHEDL,

TELCOM,

MSPLAN,

and ALARM.

External

View

1 Keyboard.

Can

be used like

the

standard

typewriter.

However, the

Tandy

200

does

have a few

special

keys. (See

Appendix

B of this

manual

for more

details.)

2 LCD Unit. The Tandy

200

display has

sixteen

lines that

allows 40

characters on

each

line.

3

POWER Switch.

Push this

switch to

turn the

power ON or

OFF. To

conserve the

batteries, the Tandy 200

automatically

turns

the power off

if

you do not use

it for 10 minutes.

4 Low Battery

Indicator.

Before the

Tandy 200's

operational batteries

become

exhausted, this

indicator

will illuminate.

5 Display

Adjustment Dial.

This control adjusts

the

contrast of the LCD

display

relative to the

viewing angle.

6 External

Power

Adapter

Connector. Connect

the

appropriate end

of

Radio Shack's

AC

Power Supply

(Catalog

Number

26-3804,

optional/extra)

to

this connector.

Connect

the other end

of

the power

supply to

a

standard

AC wall

outiet or

approved

power

strip.

1-1

Figure 1. Front View

DIR/ACP Selector.

This selector allows you to select

either

a

direct or

acoustic

coupler connection. If you are

communicating

with another

computer over the phone

Sines via the built-in, direct-connect modem, set

this switch to the

DIR position. If

you

are using the optional/extra Model

1

00

Acoustic Coupler

(26-3805),

set this selector to the ACP

positron.

RESET Switch,

if the

Tandy

200 "locks up" (i.e., the display "Ireezes"

and

all

keys seem to

be inoperative), press this

button

to

return

to

the

Main

Menu (start-up). It is not likely that the

Tandy

200 will lock-up when you are

using the built-in

applications programs,

however, it may occur with

customized

programs.

RS-232C

Connector.

Attach

a

DB-25 cable (such as Radio

Shack

Catalog

Number

26-1408) to this connector when you need to

receive or

transmit

serial information. When

communicating

directly with another Radio Shack

computer, a Null MODEM

Adapter (26-1496) is

required. An

8"

Cable

Extender

(26-T497)

may also

be required.

SYSTEM BUS

Connector. Connect

this connector to the Disk/Video

Interface

(26-3606),

using the system bus cable.

PRINTER Connector.

For

hard-copy

printouts of information,

attach

any

Radio

Shack

parallel printer to this connector,

using an optionai/extra

printer

cable.

Direct-Connect MODEM (PHONE) Connector.

When communicating with

another computer via the

Tandy

200's

built-in MODEM, connect the round

end

of the

optional/extra modem

cable to this connector.

CASSETTE Recorder Connector.

To save or load information on a

cassette tape, connect

the cassette recorder here. An

optional/extra

cassette recorder (and cable) is required.

Bar

Code

Wand

Connector. Attach the optional/extra

bar

code

wand

to

this connector. Note that special bar code

reader software is required.

o

O

o

O

O o

(D ® ®

Figure 3. Bottom View

1-3

1

MEMORY

POWER Switch. This switch is

used to

prevent

discharge of the

internal Nickel-Cadmium

battery, which is

used

for RAM back-up.

The Tandy

200 will operate

only when the power switch is

set to ON. Set this switch to

the OFF position

when the Tandy 200 will not

be used

for

a

long

period of

time.

Note that the RAM will not

be backed up when this switch is set

to

the

OFF

position.

2

Optional

ROM and RAM Compartment. An optional/extra

ROM and

RAMs can

be

inserted into

this compartment to enhance Tandy

200

capabilities.

3

Battery

compartment. When not

connected to an AC power source, the

Tandy

200 gets its power from four AA size batteries that

must be installed

in

this compartment. If the

Tandy 200 has the modification jumper

module

installed Bar Nickel-Cadmium

batteries, the battery cover is fixed

by a

tapping screw and covered

by a black sticker.

Internal

View

The Tandy

200 consists of four printed

circuit boards:

•

LCD PCB

•

Keyboard PCB

•

Main PCB

•

Memory

PCB

Potentiometer

VR1

for

MODEM

Transmitting

Level

Tone Dialer IC

Xtal

for Tone

Dialer IC

Gate Array

(SLA5080F0U)

LCDC

(HD61830B)

CPU

(80C85A)

PIO(81C55)

ROM

(BASIC,

etc.)

ROM (MSPLAN)

RAM for LCDC

Battery for

Memory

Back-up

USART

(82C51A)

Figure

4. Main

PCB

1-4

Segment Driver

Common Driver

Segment Driver

OP

Amp. for Power Supply

Figure 5. LCD PCB

Standard

RAMs

(8

K-byte

x

3)

xtal for Timer IC

Timer

IC

Reserved through

Holes

for

Modification

Jumper Module

IC Sockets for

IC

Socket for Optional ROM

Memory

Power

Switch

Optional

RAMs

Figure

6. Memory PCB

1-5

Specifications

Main

Components

Keyboard

71

keys

(9x8

matrix)

Alphabet keys

27

Number keys

10

Picture-control keys

7

Function

keys 8

Special

symbol keys 8

Mode keys

5

Other special-use

keys 6

LCD

display

Dot pitch

240

x

128

full-dot matrix

1/64

duty

1/9 bias

Dot pitch

0.8x0.8

mm

Dot

size

0,73x0.73 mm

Effective display area

191.2

(W}x101.6(D)

mm

Operation batteries

Batteries

Four type AA

Alkaline-manganese batteries

Operation time 7 days

(at

two hours/day)

(Note:

Without I/O units at normal

temperature)

Memory

protection battery (on

Main PCB)

Battery

Rechargeable battery

Back-up time About 15 days (24

KB)

About 5

days

(72

KB)

Recharge method

Trickle charge by AC adapter

or

operation

batteries

LSIs

CPU

ROM

RAM

Dimensions

Weight

80C85A

Code

and

pin compatible with 8085

Maximum 104 KB

Standard 72 KB

Option 32 KB

Maximum 72 KB

Standard

24 KB RAM

Incremental 24 KB RAM on

the

memory PCB

11 -4/5"{L)

x

8-4/9"(D)

x 2"(H)

4 lbs. 4 oz.

1-6

I/O

Interface

RS-232C

Conforms

to E1A

Standard

Signal

Communications

Protocol

Word length

Parity

Stop Bit

length

Baud rate

Maximum

transmission

distance

Drive maximum

voltage output

Drive

minimum

voltage

output

Receive

maximum

voltage

input

Receive minimum

voltage

input

MODEM/Coupler

Conforms

to BEL103

Standards

Data length

Parity

Stop bit

Full

duplex

Other

functions

Audio

cassette interface

Data Rate

Printer

interface

Conforms

to Centronics

interface

standards

Handshake

Signal

TXR {Transmit

Data)

RXR (Receive

Data)

RTS (Request to

Send)

CTS

(Ciear to Send)

DSR (Data

Set

Ready)

DTR (Data Terminal

Ready)

6,

7

or

8

bits

NON, EVEN,

ODD or IGNORE

1 or 2 bits

75, 110,

300, 600, 1200,

2400, 4800,

9600, 19200

BPS

5 meters

±

5

volts

±3.5

volts

±18 volts

±3

volts

6,

7 or 8 bits

NON,

EVEN, ODD

or IGNORE

1

or

2

bits

Answer

mode/originate

mode,

switchable

by software

Hang-up

function

Auto-diafer

function

1500 BPS

(MARK:

2400

Hz, SPACE:

1200

Hz)

STROBE,

BUSY,

BUSY

1-7

THEORY

OF OPERATION

General

This section

describes

the

theory of operation

for

the Tandy

200. Figure 7

shows how this section is organized and highlights significant

areas.

I*

CO

CJJ

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2-1

Block

Diagram

The

Tandy

200 has

four

principal LSis:

•

60C85A

CPU

This is the Central

Processing

Unit which

controls

all functions.

•

61

CSS

PIO

This

is

the Parallel Input/Output

Interface

controller

which controls the printer

interface, keyboard,

buzzer,

clock, LCD

interface

and data input of

BCR

interface.

•

82C51AUSART

This

is the

Universal

Synchronous/Asynchronous

Receiver/Transmitter

which

controls the

serial interface such as

the

RS-232C and

MODEM.

•

SLA5080FOU

Gate

Array

This

LSI

consists of the large

number of

general-purpose

gates

which are

used for the I/O

addressing,

bank selection and

other control circuits.

The

input/output

for a cassette

recorder

and the

interruption

from the BCR for

the starting data are

controlled

by

the CPU directly

through

its SOD, SID and

RST 5.5 terminals.

2-2

J/D DON TROLL Eft

E

£

8

m

3

en

2-3

CPU

The

CPU

is an 80C85A thai

runs

at a clot* speed

of 2.4576 MHz.

It is an 8-bit,

parallel

Central Processing

Unit

using C-MOS technology.

The Instruction

set is

fully compatible with the 8085A microprocessor. The 80C85A uses

a

multiplexed

data bus. The CPU bus is divided into two sections

—

the 8-bit

address bus named the A8-A15, and the 8-bit address and data bus named the

AD0-AD7,

The address and data bus are

separated

in

the SLA5080FOU

by

using the ALE signal. The functional block diagram of this circuit in the

SLA5080FOU is shown in Figure 9.

AL.E

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Figure 9.

Functional

Block Diagram of Bus Separation Circuit

Memory

The

Tandy 200

uses a 32K-byte

ROM

for the MSPLAN, 40K-byte

ROM for

BASIC and the other

application programs, and

24K-byte static

RAM to store

the data and programs.

The 40K-byte ROM

consists

of an 8K-byte ROM (M13)

and

32K-byte

ROM (M15). The 24K-byte

RAM consists of three

8K-byte

RAMs.

Furthermore, a

32K-byte

ROM and two 24K-byte

RAM packages can be used

optionally.

The 24K-byte RAM package

consists of

three 8K-byte

RAMs and

one decoder IC

{40H138), mounted

on

a

ceramic

substrate.

Figure

10 shows

the memory map

and

Figure 11 shows the

interna!

wiring

diagram of the RAM

package.

2-4

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Figure

10- Memory Map

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cs2

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Figure 11.

Internal

Wiring diagram

of

RAM

package

2-6

Address

Decoding and

Bank

Selection

Circuit

Selection

of

RAMs and ROMs

are determined by

the address and bank signals

generated

in the SLA5080F0U.

Figure

12

shows the bank

selection circuit

in

the

SLA5080FOU.

The latch AA0036

stores

the bank selection data

sent

from the CPU with the Y5

and WR signal.

The decoder AA0038 is

enabled

by the memory address

0O00H

to 9FFFH for ROMs and the

decoder

AA0037 is enabled by

the

memory

address A00OH to FFFFH

for RAMs.

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Figure 12. Bank Selection Circuit

2-7

I/O Map

Figure

13

shows the I/O address decoding circuit included in the

SLA508OF0U

that decodes

address signals

AD4-AD6.

The AD7

signal

acts as the enable

signal for the decoder AA0024 with the IO/M signal.

At the

latch AA0063, the

chip

enable

terminals G1 and G2 are connected to the ALE signal

passing

through

the inverter,

because the AD0-AD7 signals are the multiplexed

bus.

The

I/O

map and I/O port description are shown In Figure 14.

The

port

assignment of the 81C55 is shown In

Table

1.

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I/O Map

and I/O

Port Description

2-9

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Table 1. Port Assignment

of

trie

81C55

2-10

Keyboard

Key

strobe

signals

are

emitted

from

the PBO

and PA0-PA7

terminals

of the

81C55,

and the

return

signals

from

the

keyboard_pass

through

the

octal bus

buffer

(M27) which

is

enabled

by

NANDing

the

RD

and STB/K

signals

at M29,

and then

the return

signafs are

sent to the

CPU.

The

STB/K

signal

is

generated

in the

SLA5080F0U

when the

CPU

assigns

EO-

EFH to

the I/O

port

address.

The CPU

starts the

key

scan

operation

when

the

RST

7.5 interruption

is

accepted.

This

interruption

(TP

signal)

is

generated

about

every

3.3 msec,

at M34 by

dividing

the

CLK signal

(2.4576 MHz).

Condition

ol

pressing

"T"

key is

shown

in Figure

15.

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fl-

I a. I fl. i o_ .a*

a. a.

a,

Hf

m|

u>y c-y

Jj uij

»["[

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3

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=

i

=

3

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Z)

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r

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a.

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0. 0-

Figure

15.

Condition

of Pressing

"T" Key

2-11

Cassette

Interface

Circuit

The

cassette

interface circuit

Is subdivided

Into three

sections:

•

Write

Circuit

•

Read

Circuit

•

Remote

Circuit

Write

Circuit

The

write

circuit

is accomplished in

several steps. First, the

serial data from the

SOD terminal

of the CPU

Is Inverted

by M1. Then,

the

DC component

Is

removed

by

C3.

And

finally,

the data

passes through an integrator

consisting

of

R8

and

C2,

and

after voltage division,

out to a cassette

recorder

AUX jack.

Figure

16

shows

the

write circuit

of

the

cassette interface.

-oo

I—

SIOD

PUI

rLTLTLn

Figure

16. Write Circuit of

Cassette Interface

Read

Circuit

The

signal

input from the

earphone

jack of the cassette recorder

passes

through

the clamp circuit

consisting

of D1 and D2, and then is input

to

the

comparator

circuit

consisting of M2.

Finally, the

signal is converted

into the digital signal

and sent

to

the SID

terminal

of the

CPU. Figure 17 shows the

read circuit.

In

the circuit,

DS clamps the negative

voltage

output

of

the comparator.

CN2

VDO

rLTLTLTI

Figure

17.

Read Circuit

of

Cassette Interface

2-12

Remote

Circuit

By writing-in data

"1

" into bit 1 of the output

port specified

by EO-EFH, the

REMOTE

terminal

of

the SLA5O8OF0U Is

changed

to "H." Then T1

1

Is switched

ON and

RY1

Is

energized. This

controls

the motor of the cassette

recorder.

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i5E

51

TO

c

v5

TO

75

rS

o o

3

D

-.)

eTcss

9TBP

lS5

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AAOtHfl

C Q

D Q

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L>

ffEWOTE

Dt

Gat*

Arraj

SLA50BOFou

Figure

18. Remote Circuit of

Cassette

Interface

Printer Interface

Circuit

The printer Interface

circuit conforms to

Centronics

standards. As

shown in

Figure

19,

the

BUSY

signal from the

printer is

read from the PC2

of

the 81C55.

If

the

condition Is

not busy (PC2

=

"L"), the 8-bit

parallel data

(PA0-PA7

from

81C55)

is

sent to the

printer.

Then, by writing-in

data

"1"

into bit 1 of

the output

port specified by I/O

address

EO-EFH, the

PSTB

signal is generated

in the

SLA5080FOU

and sent

to the

printer.

As soon as the

printer

receives this PSTB

signal, the BUSY

signal is

changed

to

"H" indicating that the

printer is

busy.

The CPU

then

waits lor a while

until

this BUSY

signal becomes "L"

As soon

as the

printer

prints the one

character

specified

by

the 8-bit

paralle! data,

the BUSY

signal

becomes "L"

Then, the

CPU sends the

If the printer is in

ON

LINE condition, the

BUSY

signal is "H" and

sent to

the

CPU,

passing

through the PC1

of the

81C55.

But,

when in the

OFF LINE

condition, the BUSY

signal is "L" and

transmission of

print

data to

the printer is

inhibited by the CPU.

2-13

YO

y

Y

2

>

—

--....

V3

5

^»-

Gale

Array

SLASOBGFQU

#

Figure 19.

Printer

Interface Circuit

Bar Code Reader Interface

Circuit

The input signal Irom the bar code

reader is subjected to

waveform shaping,

inverted

by the

Schmitt-type

inverter (M1),

and

then sent to the PC3 terminal of

the

81C55

and the

RST

5.5

terminal of the CPU.

When the

bar code

reader reads

the first white part of the bar code, a "L" level

signal

is generated,

then inverted by M1

.

As soon as RST 5.5 interruption

occurs, the CPU starts the data input operation,

passing

through

the PCS of the

81C55. As the bar code reader is moved

across the bars,

"H"

and

"L"

signals

(which

correspond

to

white

and

black bars respectively) are generated

continuously

and

Inversion signals are sent to the PC3 of the 81C55 as the

serial input data. Refer to Figure 20.

2-14

Radio Shack Tandy 200, 26-3861 Technical Reference Manual

Specifications and Main Features

Frequently Asked Questions

User Manual