Renesas H8 Series, User Manual

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11
2.6.6 Voltage Follower Circuit
CAUTION
1. Do not connect the user system interface cable to the emulator
without user system connection.
2. Turn on the user system before starting up the emulator.
A voltage follower circuit is implemented on the emulator which allows the user system voltage level from the
user system to be monitored. This monitored voltage level is automatically supplied to the logic on the emulator
and is derived from the emulator power supply unit. This means that no power is taken from the user system
board.
If no user system interface cable is connected to the emulator, the emulator will operate at a specified voltage
and all clock frequencies will be available to the user. If the user system interface cable is attached, the emulator
will match the voltage supplied to the user target in all cases; i.e. even when the user V
CC
is below the operating
voltage for the MCU. You must be careful not to select an invalid clock frequency. When the emulator is
connected to the user system and the user system is turned off, the voltage follower circuit output voltage level is
0 V. In this case, the emulator will not operate correctly.
You can set a user V
CC
threshold in the range Vcc max. – 0 V by using the emulator configuration dialog box. If
the user V
CC
drops below this threshold, [User System Voltage] in the [Extended Monitor] window will display
Down , otherwise OK is displayed.
User
threshold
User Vcc
threshold
The user system interface
cable is not connected.
User Vcc level
E6000
Vcc level
3.3 V
0 V
OK
Down
3.3 V
0 V
Figure 2.10 Voltage Level Monitoring (Example for Vcc = 3.3 V)