MPLAB
®
ICE 2000
DS51140J-page 4 2004 Microchip Technology Inc.
4.3.2 CLOCK SOURCE FROM THE TARGET
APPLICATION
If the Target Application is selected to provide the clock
source, the target board must also be selected to
power the emulator processor (see the MPLAB ICE
2000 on-line help file in MPLAB IDE (Help>Topics
) or
the MPLAB ICE 2000 User’s Guide (DS51488), “Using
a Target Board Clock”).
At low voltage, the maximum speed of the processor
will be limited to the rated speed of the device under
emulation.
An oscillator circuit on the device adapter generates a
clock to the processor module and buffers the clock
circuit on the target board. In this way, the MPLAB ICE
2000 emulator closely matches the oscillator options of
the actual device. All oscillator modes are supported
(as documented in the device’s data sheet) except as
noted in Section 3.0 Emulator-Related Issues. The
OSC1 and OSC2 inputs of the device adapter have a
5 pF to 10 pF load. Be aware of this when using a
crystal in HS, XT, LP or LF modes, or an RC network in
RC mode.
The frequency of the emulated RC network may vary
relative to the actual device due to emulator circuitry. If
a specific frequency is important, adjust the RC values
to achieve the desired frequency. Another alternative
would be to allow the emulator to provide the clock as
described in Section 4.3.1 Clock Source from
Emulator.
When using the target board clock, the system’s
operating voltage is between 2.5V and 5.5V.
4.4 ESD Protection and Electrical
Overstress
All CMOS chips are susceptible to electrostatic
discharge (ESD). In the case of the processor modules,
the pins of the CMOS emulator are directly connected
to the target connector, making the chip vulnerable to
ESD. ESD can also induce latch-up in CMOS chips,
causing excessive current through the chip and possi-
ble damage. MPLAB ICE 2000 has been designed to
minimize potential damage by implementing over-
current protection and transient suppressors. However,
care should be given to minimizing ESD conditions
while using the system.
During development, contention on an I/O pin is
possible (e.g., when an emulator pin is driving a ‘1’ and
the target board is driving a ‘0’). Prolonged contention
may cause latch-up and damage to the emulator chip.
One possible precaution is to use current limiting
resistors (~100 Ω) during the development phase on
bidirectional I/O pins. Using limiting resistors can also
help avoid damage to modules, device adapters and
pods that occurs when a voltage source is accidentally
connected to an I/O pin on the target board.
4.5 Freeze Mode
The MPLAB ICE 2000 system allows the option of
“freezing” peripheral operation or allowing them to
continue operating when the processor is halted. This
option is configured in the MPLAB IDE. The Freeze
function is available on all processor modules except
the PCM16XA0.
This function is useful to halt an on-board timer while at
a break point. At a break point and while single
stepping, interrupts are disabled.
5.0 DEVICE ADAPTER ISSUES
This section details processor-specific considerations
that have been made on device adapters. Only
adapters with special considerations are listed.
There will be a max of 10 mA of current draw from the
target system even when the emulator processor mod-
ule is being powered by the emulator system, and
running internal clock. This is due to components on
the device adapter being powered by the target board.
