Voltage Reference High Select Header (W3) - Motorola M68MPBF333 User Manual

2.2.3

Voltage Reference High Select Header (W3)

Jumper header W3 selects the voltage reference high (VRH) source: either MPB
power (VDDA) or an external VRH source. The drawing below shows the factory
configuration: a fabricated jumper on pins 1 and 2. This configuration selects
VDDA as the VRH source.
To use an external VRH source, first place the fabricated jumper on W3 pins 2
and 3. Then connect the MCU VRH pin to the external VRH source. Each
configuration defines the best method for connecting the MCU VRH pin to the
external VRH source:
• MPB/MPFB – connect via the MPFB logic analyzer connector (refer to
Chapter 4 for the appropriate logic analyzer pin).
• MPB/MMDS1632 – connect via the VRH pin of the target MCU socket.
• MPB/Target System – connect via the VRH pin of the target system
MAPI bus.
Alternately, you may remove the jumper and wire-wrap directly to W3 pin 2.
Connecting directly to pin 2 is an option regardless of the configuration.
M68MPB333UM/D
HARDWARE PREPARATION AND INSTALLATION
W3
1
2
3
2-7