Cartridge Connector - Tandy 26-3334 Service Manual

5.12
Cartridge Connector
(CN1)
A
40-pin cartridge connector provides
the
possibility
of
expanding
the
TANDY Color Computer
3
in almost any
manner. All
of the important CPU bus
signals are tied
to this connector. A
complete list and brief description
of these signals
is
provided
in Table
3.
The most common usage
of the
cartridge connector
is
with
the
ROM
cartridge. For cartridge detection,
the Q
clock
is
connected
to the
cartridge interrupt
pin, which
generates
an
interrupt anytime
the
cartridge
is
plugged
in and forces
the
computer
to
jump
to the
program
in ROM.
CAUTION
DO NOT PLUG A CARTRIDGE
IN
WITH POWER
APPLIED TO THE COLOR COMPUTER
AS SERIOUS
DAMAGE TO THE UNIT AND /OR
THE CARTRIDGE MAY RESULT.
In
addition
to the
expected
data,
address and R/W* lines, several
control and special purpose signals
are available
on the
cartridge
connector. They
are
as
follows:
HALT* -
This active-low signal
places
the processor
in a
HALT state immediately
following
the
execution
of
the current instruction.
While
in the HALTed
state,
the processor address
and
data
lines are in the high
impedance mode, making
it
possible
for external devices
to
access RAM and ROM. The
processor may
be
HALTed
indefinitely without
any loss
of internal data.
NMI* -
This
is the
non-maskable
interrupt input
to
the CPU.
RESET*- This
is
the
master system
reset and power-up clear
signal.
E,
Q
- These
are the two
clock
signals
for the
MC68B09E
CPU.
CART*
- This
is
an interrupt input
into
PIA
IC4.
It is
used to
detect
the
presence of
a
cartridge.
CTS* -
This
is the
Cartridge
Select Signal.
It is
valid
when
the
processor reads any
location from C000 Hex
to
DFFF
Hex, as long
as the ACVC
is
in Map Type
0.
Note
that
it
is
not active while
writing
to
these locations.
SND
-
This signal
is
connected
directly
to the
sound input
of the DAC chip and allows
cartridge-generated
sound
signals
to be fed through
the
TV sound system. The signal
should be AC coupled and
should not exceed 3.9 volts
p-p.
SCS*
-
This
is a
second chip-
select signal from
IC9.
It
is
active
for both reads from
and writes
to
addresses,
FF40H through FF5FH,
regardless
of the map
type.
SLENB*-
This signal disables
the
internal device selection.
This allows decoded but
unused sections
of
memory
to
be
used
by the cartridge
hardware
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