78M6613 Data Sheet
DS_6613_018
3.4 Connecting 5V Devices
All digital input pins of the 78M6613 are compatible with external 5V devices. I/O pins configured as
inputs do not require current-limiting resistors when they are connected to external 5V devices.
3.5 UART (TX/RX)
The RX pin should be pulled down by a 10 kΩ resistor and optionally protected by a 100 pF ceramic
capacitor, as shown in Figure 10.
Optional
78M6613
10kΩ
100pF
RX
RX
TX
TX
Figure 10: Connections for the RX Pin
3.6 Reset Function and Reset Pin Connections
The 78M6613 requires an external reset circuit to drive the RESET input pin. The reset is used to
prevent the 78M6613 from operating at supply voltages outside the recommended operating conditions.
Reset ensures the device is set to a known set of initial conditions and that it begins executing
instructions from a predetermined starting address.
The reset can be forced by applying a high level to the RESET pin. The reset input is internally filtered
(low-pass filter) in order to eliminate spurious reset conditions that can be triggered in a noisy
environment. For this reason the RESET pin must be asserted (high) for at least 1μs in order to initiate a
reset sequence.
The external reset circuitry should be designed in order to hold the RESET pin high (active) whenever
V3P3D is below normal operating level. Refer to Section 4.3, Recommended Operating Conditions.
Figure 11 shows the behavior of the external reset circuitry.
16
Rev. 1.1
TERIDIAN [ TERIDIAN SEMICONDUCTOR CORPORATION ]
