The 68000 transmits data and control
to
and from the peripherals via the parallel
110
and the 3 custom chips.
1M
is
the processor clock to the 68000.
Cl
, C3 and CDAC are used to clock the
custom chips and determine the timing
of
signals to the memory arrays.
ROM
The ROM contains the kernel and DOS routines; it
is
128K x
16.
Parallel I/O
The 2 mUltipurpose 8520
110
chips provide the following:
110
to and from the parallel port connector
Control lines to and from the joystick/mouse ports
A control line to the front panel LED
Internal control lines
Keyboard control lines , clock and data
Serial port control lines
Floppy disk interface control lines
Internal timers
These 2 chips reside on the 68000 buses and are read and written by the 68000.
Clocks Generator
The entire computer board
is
run synchronous to the 3.579545 MHz color clock.
This
is
accomplished by generating a number
of
submultiple frequencies from
the master
28
.63636 MHz NTSC (or 28.37516 MHz for PA) crystal oscillator.
All clocks are generated by the Fat Agnus custom chip. The following are the
primary clocks:
CI 3.579545 MHz color clock
C3 C2 shifted
45
degrees later
7M C I XORed with C3
= 7.15909 MHz
CDAC 7M shifted 90 degrees later
Technical Reference A-13
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