Datasheet

MPC8245 Integrated Processor Hardware Specifications, Rev. 10
48 Freescale Semiconductor
System Design
reset sources, such as voltage monitors, watchdog timers, power supply failures, or push-button switches,
the COP reset signals must be merged into these signals with logic.
The arrangement shown in Figure 26 allows the COP port to independently assert HRESET
or TRST,
while ensuring that the target can drive HRESET
as well. If the JTAG interface and COP header will not
be used, TRST
should be tied to HRESET through a 0-Ω isolation resistor so that it is asserted when the
system reset signal (HRESET
) is asserted, ensuring that the JTAG scan chain is initialized during
power-on. Although Freescale recommends that the COP header be designed into the system as shown in
Figure 26, if this is not possible, the isolation resistor will allow future access to TRST
in the case where
a JTAG interface may need to be wired onto the system in debug situations.
The COP interface has a standard header for connection to the target system based on the 0.025"
square-post, 0.100" centered header assembly (often called a Berg header). Typically, pin 14 is removed
as a connector key.
There is no standardized way to number the COP header shown in Figure 26. Consequently, different
emulator vendors number the pins differently. Some pins are numbered top-to-bottom and left-to-right
while others use left-to-right then top-to-bottom and still others number the pins counter clockwise from
pin 1 (as with an IC). Regardless of the numbering, the signal placement recommended in Figure 26 is
common to all known emulators.