Zenith Z-171 Series Service Manual page 17

Page
1-11
Introduction and General Information
Control signals and timing - Responsible for generating the signals
and clock pulses that are required for proper coordination of the com-
puter.
Disk drive control - Composed of both digital and analog sections
which are responsible for encoding and decoding all information to
and from the floppy disk drives and for controlling the operation of
the drives themselves.
InpuVoutput circuits - Provides for the interfacing between the CPU
and external peripherals.
Keyboard
proc~ssor
- Uses an 80C39 microcontroller to perform the
keyboard scan functions and acknowledge interrupts to the CPU.
DC power board - Distributes the power supply voltages to the LCD
assembly, disk drives, main logic board, and the RGB video board.
LCD decoder/driver board - Generates an 80-column by 25-line display
of the information written to it by the main logic board. This board also
generates both the IBM compatible low-resolution and the high-resolution
graphics on the LCD.
High-resolution video logic board- Produces both composite and RGB
high-resolution outputs which are available at the back panel video con-
nectors of the computer for connection to an external composite or RGB
monitor. This optional card is plugged into the main logic board.
System RAM card - Contains the system RAM. This memory is used
to store all programs and data that are in process. I t can be configured
with 64-kilobit and/or 256-kilobit memory devices providing several si2es
of system memory ranging from 128K to 640K.
Disk drives - Used to access the information stored on the floppy disk.