AN_6612_007
78M6612 Hardware Design Guidelines
Rev 2
13
5.4 In Circuit Emulator (ICE) Pins
The 78M6612 evaluation boards employ a reduced component ICE interface. This circuit design is
sufficient when short ICE cables (less than 12 inches) are used or large RF fields are not present. If either
case is not true, the following recommendations are to be utilized.
If the ICE pins are used to drive LCD segments, attach 22 pF capacitors from the ICE signals to GND for
EMI protection. If the trace length of the ICE signals exceeds 2 inches, add 22 pF capacitors across the
ICE signals to GND for EMI protection. If the external ICE cables exceed 12 inches, insert the series
resistors to control signal reflections.
Connect the ICE_EN pin to GND on production boards using pre-programmed 78M6612 devices.
Otherwise, provide a strong pull-down resistor (recommend 330
Ω
value) along with a filter capacitor of
1000 pF on ICE_EN to allow in-circuit programming.
Figure 11: ICE Pin Used to Drive LCD Segments
5.5 Connecting 5 V Devices
All digital input pins (DIO pins) of the 78M6612 are 5 V compatible allowing connection to external 5 V
devices. I/O pins configured as inputs do not require current-limiting resistors when they are connected to
external 5 V devices.
E_RST
E_RXTX
E_TCLK
62
Ω
62
Ω
62
Ω
22pF
22pF
22pF
LCD Segments
(optional)
ICE_E
E_RST
78M6612
E_RXTX
E_TCLK
62
Ω
62
Ω
62
Ω
22pF
22pF
22pF
LCD Segments
(optional)
ICE_E
V3P3
