Voltage Reference Low Select Header (W4); Vssa Insertion Point (E1) - Motorola M68MPB916X1 User Manual

2.2.4

Voltage Reference Low Select Header (W4)

Jumper header W4 selects the voltage reference low (VRL) source: either MPB
power (VSSA) or an external VRL source. The drawing below shows the factory
configuration: a fabricated jumper on pins 1 and 2. This configuration selects
VSSA as the VRL source.
To use an external VRL source, first place the fabricated jumper on W4 pins 2 and
3. Then connect the MCU VRL pin to the external VRL source. Each
configuration defines the best method for connecting the MCU VRL pin to the
external VRL 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 VRL pin of the target MCU socket
• MPB/Target System – connect via the VRL pin of the target system MAPI
bus
Alternately, you may remove the jumper and wire-wrap directly to W4 pin 2.
Connecting directly to pin 2 is an option regardless of the configuration.
2.2.5

VSSA Insertion Point (E1)

Insertion point E1 is a plate through hole that lets you connect an external ground
to the MPB VSSA pin (refer to paragraph 2.2.2). Insert an external ground wire in
E1 and solder it into the plate through hole.
M68MPB916X1UM/D
HARDWARE PREPARATION AND INSTALLATION
VRL Source
Selection
1
2
3
W4
NOTE
Insertion point E1 is not populated by the factory.
Fabricated
Jumper
2-7