FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
The VSUP should be left open or forced to a value equal
to or above V.
MCU FLASH PROGRAMMING CONFIGURATION
To allow for new software to be loaded into a SBC’s MCU
NVM or to standalone EEPROM or Flash, the 33742 is
capable of having (1) VSUP applied to it to from an external
power 5.0 V supply and (2) having the RST and the WDOG
outputs pins eternally forced to 0.0 V or 5.0 V without
damaging the device.
The VDD regulator uses an internal pass transistor
between VSUP and the VDD output pin. Biasing the VDD
output pin with a voltage greater than VDD potential will force
current through the body diode of the internal pass transistor
to the VSUP pin.
The RST pin is periodically pulled LOW for the tRSTDUR
time (device in Reset mode), before being pulled to VDD for
350 ms typical (device in Normal Request mode). During the
time reset is LOW, the RST pin sinks 5.0 mA maximum
(IPDW).
This allows the SBC to be externally powered and off-
board signals to be applied to the reset pins. No functions of
the 33742 are operating. Figure 18 illustrates a typical
configuration for the connection of programming and
debugging tools.
VDD
VSUP (Open or > 5.0 V
RST
MCU with
33742
WDOG
Flash Memory
Programming Bus
Programming Tool
5.0 V
Note External supply and sources applied to VDD, RST, and WDOG test points on application circuit board.
Figure 18. Simplified Schematic for Microcontroller Flash Programming
33742
Analog Integrated Circuit Device Data
Freescale Semiconductor
32
FREESCALE [ Freescale ]
