Epson PX-8 - CPU Operations

REV.-A
2.3 CPU Operations
Control of memory, I/O, and various other functions is distributed among the three COMS CPUs
on
the MAPLE board.
(1)
Main CPU (Z80) ..... 2.45 MHz
The main CPU provides overall control of circuit operations using the external 32 kB ROM
(2A).
Its major control functions are:
• Expand interface (CN8)
control
• RS-232C interface operation control via a serial controller
• 64 kB dynamic RAM read/write and refresh operation control via a gate array (GAH40D)
• RS-232C interface control via a serial controller (82C51 )
•
RS-232C clock supply via a baud rate generator (GAH40M)
(2) Sub-CPU (7508) ..... 200 kHz
The sub-CPU
provides the following circuit operation control functions independent of the
main CPU using the internal 4 kB masked ROM:
•
Command exchange with the main CPU via a gate array (GAH40M)
• Power on/off control
• Change mode (normal or trickle) control
• Keyboard data entry check
• DIP
switch setting read
•
A-D converter enabling/disabling control
(3) Slave CPU (6303) ..... 614 kHz
The
6303 provides the following control functions independent of the main CPU, using the in-
ternal 4 kB masked ROM:
•
Command exchange with the main CPU via the LCD controller (SED1320)
• Microcassette control via a gate array (GAH40S)
• High speed serial interface
control
• Speaker output control
• LCD display control via the LCD controller (SED1320)
• ROM capsule read control via a gate array (GAH40S)
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