Emulation Design Considerations
15-21
Designing for JTAG Emulation
Figure 15–10. EMU0/1 Configuration With Additional AND Gate to Meet Timing
Requirements
Open
Collector
Drivers
EMU0/1-IN
Backplane
Target Board m
TCK
XCNT_ENABLE
Pullup Resistor
To Emulator EMU0
PAL
Pullup
Resistor
Open
Collector
Drivers
Target Board 1
EMU0/1
Pullup Resistor
EMU1 signal from other boards
EMU1
AND
To Emulator EMU1
Circuitry required for >25-ns rising/
falling edge modification
EMU0/1-OUT
. . .
Device
Device
EMU0/1
. . .
. . .
. . .
. . .
. . .
. . .
1
n
Device
Device
1
n
Up to
m boards
Notes:
1) The low time on EMUx–IN should be at least one TCK cycle and less than 10
m
s. Software will set the EMUx–OUT
pin to a high state.
2) To enable the open-collector driver and pullup resistor on EMU1 to provide rising/falling edges of less than 25 ns,
the modification shown in this figure is suggested. Rising edges slower than 25 ns can cause the emulator to detect
false edges during the RUNB command or when the external counter selected from the debugger analysis menu
is used.
Figure 15–11.
Suggested Timings for the EMU0 and EMU1 Signals
EMU0/1-IN
EMU0/1-OUT
TCK