T W R - S 0 8 L L / L H U S E R G U I D E
A P R I L 2 7 , 2 0 1 0
U S E R G U I D E
10
LOW VOLTAGE RESET
The target MCU applies an internal Low Voltage Detect (LVD) circuit. The LVD holds the MCU
in reset until applied voltage reaches an appropriate level. The LVD also protect against
under-voltage conditions. Consult the target device RM for details on LVD operation.
TIMING
The TWR-S08 uses the MC9S08LL or MC9S08LH internal timing source by default. An
external 32 kHz XTAL oscillator, configured for low-power operation, is also provided. Consult
the target device RM for details on configuring the selected timing source.
COMMUNICATIONS
The TWR-S08 board supports serial communications through an on-board, low-voltage, RS-
232 physical layer transceiver
(PHY) connected to a 2x5, 0.1”, pin header. The PHY supports
valid RS-232 signaling for input voltage levels down to +1.8V. The COM_SEL header selects
the serial path applied.
NOTE:
The COM_SEL header allows the SCI signals to be routed to the OSBDM.
However, the OSBDM does not support serial communications at this time.
RS-232
An RS-232 translator provides RS-232 to TTL/CMOS logic level translation on the COM
connector. The COM_PORT connector is a
2x5, 0.1”, pin header. Communication signals
TXD1 and RXD1 are routed from the transceiver to the MCU. Hardware flow control signals
RTS and CTS are available on the logic side of the transceiver. These signals are routed to
vias located near the transceiver. RTS has been biased properly to support 2-wire RS-232
communications. Figure 4 below shows the COM signal connections.
Figure 4: COM Signal Connections
MCU Signal
COM Signal
PTC1/TXD
TXD
PTC0RXD
RXD