• Receives Master Clock from Motherboard and generates Phase 1 (Φ1
or Ph 1) and Phase 2 (Φ2 or Ph 2) clocks used to synchronize the
entire system.
• Transmits "Refresh" signal at least every 2 milliseconds to refresh
the dynamic RAM memory chips on the RAM Memory pcb.
• Receives the four "trigger" lines from the fire button of the hand
controller accessories.
• Receives the lines from the four control switches to the right of
the Keyboard:
Option - Selects a variation of the Program Cartridge
Select - Selects a different portion of the Program Cartridge
Start - Starts a program (usually on the Program Cartridge)
System Reset - Resets the system
• Generates video signals to be processed by the Motherboard before
being sent to R.F. Module on the Power Supply pcb.
4.2.3. ROM Personality pcb
The ROM Personality pcb contains in read-only memory (ROM), the
program of operating instructions for the microprocessor. Two 4K ROMs
contain the Operating System, and one 2K ROM contains arithmetic
functions for use with BASIC programming. Information is retreived
from the ROMs by addressing a particular location on the ROM using
the Address bus. The data contained in that location is placeed on
the Data Bus to be read by the microprocessor.
The ROM Personality pcb also provides the Chip Select signals used to
select the various LSI chips throughout the Console system and for
the bidirectional data buffers on the Motherboard.
4.2.4 RAM pcb
The RAM (Random Access or Read/Write Memory) pcb performs the
function of temporary data storage for the System. The RAM is dynamic
RAM, requiring refresh, and comes in 8K or 16K versions.
Each RAM chip on the RAM pcb has only seven address lines. To address
16K separate locations requires fourteen address lines. To accomplish
this, a fourteen-bit address is sent to the address demultiplexer,
which first passes the lower seven bits to the RAM chips as a Row
Address.
ATARI Personal Computer 4-3
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