Radio Shack TRS-80 Service Manual page 60

Color Computer 2
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Service Manual
The most common use 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 2 AS SERIOUS
DAMAGE TO ·rHE UNI'r 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 MC6809E CPU.
CART* -- This is an interrupt input into PIA U2. 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 COOO Hex to FEFF
Hex, as long as the SAM is in Map Type 0. Note that it is
not active during a write to these locations.
SND -- This signal is connected directly to the
of the DAC chip, and allows cartridge-generated
signals to be fed through the TV sound system.
should be AC coupled, and should not exceed 3.9
sound input
sound
The signal
volts p-p.
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