IP2022 User’s Manual—In-System Debugging www.ubicom.com 349 These signals are described below: • DVdd,   IOVdd,   GND   (Power   and  Ground)—If  the   debug-
ger/programmer draws power from the target system, then:
–  The debugger/programmer must function on any voltage
in the range from 2.3 to 3.6V. The current requirements of
the debugger/programmer must be published by the ven-
dor. –  The debugger/programmer may use the IOVdd pin as the
logic supply rail when driving the target microcontroller,
therefore  the  specification  that  IOVdd  will  not  exceed
3.6V. –  There is no disadvantage in a debugger/programmer be-
ing able to operate with an IOVdd voltage greater 3.6V as
long  as  it  is  capable  of  running  with  an  IOVdd  voltage
down to 2.3V and does not violate the maximum logic high
voltage of 3.6V. –  Current drawn from the target circuit should be minimal to
minimize the influence of the debugger on the target sys-
tem. If the debugger/programmer is capable of supplying power to
the circuit under test, then the user must be provided with the
ability to turn off this feature so that it does not interfere with a
circuit under test that is self-powered and provides IOVdd to
the ISD/ISP interface. Additionally, the debugger/programmer
must not be damaged when this featured is enabled and the
target system provides IOVdd to the ISD/ISP interface. If the
debugger/programmer is capable of supplying an adjustable
regulated voltage to the IOVdd pin, then there is no require-