Radio Shack TRS-80 Model III Operation Manual page 4

MODEL II OPERATION
Keyboard
The Model II Keyboard has its own LSI controller to free the Z-80A processor
from keyboard scan and related tasks. The Keyboard is in a separate case and
is connected to the Display Console via a built-in cable at the bottom front of
the Console.
The Model II has the standard typewriter keys (letters, numbers and
punctuation symbols); however, each ofthese keys can output several
different codes to the Computer, depending on which mode the Keyboard is
in: Unshift, Shift, Caps, or Control. In addition, the Keyboard features a
Repeat key and two programmable "function" keys. (See
Keyboard
Operation. )
Floppy Disk Drive
The Model II includes a built-in 8" disk drive. Up to 3 more drives can be
added in an external Expansion Unit. (See Section 6,
Add-Oos.)
Because of a
special high-density recording technique, each diskette can contain 509,184
bytes of information, which is more than 5 times the capacity of a 5-1/4"
diskette. (It would take a 70 wpm typist 24 hours of typing at speed to fill an 8"
diskette.)
Note: Actual space available to user is determined by the Operating System.
The "System Drive" (the one that's built-in) must always contain an Operating
System diskette. The other optional drives can de devoted exclusively to the
storage of user programs and data. (See the
Disk Operating System Manual
for actual diskette space allocation.)
Peripheral Interfaces
There are four interface connections on the back of the Display Console:
• Two serial (RS-232-C) Input/Output (I/O) channels
• A parallel I/O channel, e.g., for connection to TRS-80 standard
parallel-interface line printers
• Floppy-disk I/O channel for connection of the Model II Disk Expansion
Unit
The Display Console also provides connectors and slots for future expansion.
(See Section 6,
Add-Oos.)
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