System Overview; Block Diagram - Radio Shack TRS-80 Model 4 Technical Reference Manual

1.1 SYSTEM OVERVIEW

The Radio Shack TRS-80 Model 4 Microcomputer is an enhanced version of Radio Shack's popular TRS-80 Model
Ill Microcomputer. The TRS-80 Model 4 is software compatible with the Model Ill so that owners of either system
can take advantage of the large number of programs available.
Features of the TRS-80 Model 4 which are common to the TRS-80 Model III include:
•
Availability of Level I or Level II BASIC in ROM
•
Full size typewriter style keyboard
•
A 12-inch video display
•
Built-in cassette interface
•
Character display of 16 lines of 64 characters
•
Graphics under control of BASIC (128 H x 48 V)
•
UL recognized construction
•
12-key numeric keypad for rapid entry of numbers
•
Rugged cabinet housing keyboard, electronics, video display, and power supply
•
Direct drive video monitor for improved resolution
•
Internal power supply
•
Parallel printer port for use with Radio Shack printers
Other features available when Level II BASIC is used are: real time clock, upper and lower case characters, RAM
internally expandable to 128K bytes, I/O port for peripheral expansion, and cassette interface available with 500
and 1500 baud rates.
Optional peripherals for the TRS-80 Model 4 include disk drives (two built-in, two external) with double density for
increased storage capacity, and a built-in RS-232 serial interface for communications and peripheral interface.

1.2 BLOCK DIAGRAM

The Block Diagram (Figure 1-1) shows the various internal components and connections of the Model 4
Microcomputer.
INTRODUCTION
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