Block Diagram - Tandy 102 Service Manual

Block Diagram
The Tandy 102 has three principal LSIs.
• 8OC85A CPU
This is the Central Processing Unit which controls all functions.
• 81 C55 PIO
This is the Parallel Input/Output interface controller which controls the printer interface,
keyboard, buzzer, clock and LCD interface.
• 6402 UART
This is the Universal Asynchronous Receiver Transmitter which controls the serial interface
(RS-232C or MODEM).
The input/output for a cassette recorder and the input of the BCR are controlled by CPU directly
through its SOD, SID and RST5.5 terminals.
ROM and RAMs are connected to the system bus. ROM is available only for alternative selection
from Standard or Option.
CPU
8OC85
CASSETTE
INTERFACE
ROM
32KB
STANDARD
RAM
8KB
FKEYBOARD
PC
B
I
KEYBOARD i
PIO
PRINTER
81 C55
INTERFACE
RAM
8KB
RAM
8KB
I
i
LCD
CONTROL
I I
I RAM
8KB
OPTION
ROM
32KB
OPTION
LCD P
U A RT
6402
SYSTEM BUS
SOCKET
Figure 4-2. System Block Diagram
CLOCK
LCD yPD1990AC
RS-232C
INTERFACE