16 in-circuit emulation (ice) signals, In-circuit emulation (ice) signals -11 – Motorola MC68VZ328 User Manual
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In-Circuit Emulation (ICE) Signals
Signal Descriptions
2-11
2.16
In-Circuit Emulation (ICE) Signals
The ICE module is designed to support low-cost emulator designs using the MC68VZ328 microprocessor.
There are four interface signals that are extended to external pins.
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HIZ/P/D/PG3—High Impedance, Program/Data, or Port G bit 3. During system reset, a logic low
of this input signal will put the MC68VZ328 into Hi-Z mode, in which all MC68VZ328 pins are
three-stated after reset release. For normal operation, this pin must be pulled high during system
reset or left unconnected. This pin defaults to GPIO input pulled high, but can be programmed as
the P/D function. P/D is a status signal that shows whether the current bus cycle is in program space
or in data space during emulation mode.
•
EMUIRQ/PG2—Emulator Interrupt Request or Port G bit 2. During system reset, a logic low of this
input signal will put the MC68VZ328 into emulation mode, which is described in Chapter 16,
“In-Circuit Emulation.” For normal operation, this pin must be pulled high during system reset or
left unconnected. After system reset, this pin defaults to an EMUIRQ function in normal or
emulation mode. EMUIRQ is an active low, level 7 interrupt input signal.
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EMUBRK/PG5—Emulator Breakpoint or Port G bit 5. During system reset, a logic low of this
input signal will put the MC68VZ328 into bootstrap mode, which is described in Chapter 17,
“Bootstrap Mode.” For normal operation, this pin must be pulled high during system reset or left
unconnected. After system reset, this pin defaults to the EMUBRK function, which is an I/O signal
used in emulation mode for breakpoint control.
•
EMUCS/PG4—Emulator Chip-Select or Port G bit 4. EMUCS is an 8-bit data bus width chip-select
signal that selects the dedicated memory space from 0xFFFC0000 to 0xFFFDFFFF. It cannot be
used to select 16-bit data bus memory devices. EMUCS is not only activated in emulation mode,
but in normal and bootstrap modes as well. See Chapter 16, “In-Circuit Emulation,” for more
information about EMUCS operation. This pin defaults to an EMUCS signal.