DEMO908QB8 Freescale Semiconductor, DEMO908QB8 Datasheet - Page 14

• Manufacturer Part Number: DEMO908QB8
• Description: BOARD DEMO FOR MC68HC908QB8
• Manufacturer: Freescale Semiconductor
• Type: MCUr

Specifications of DEMO908QB8

• Contents: *
• Processor To Be Evaluated: MC908QB8
• Data Bus Width: 8 bit
• Interface Type: RS-232, USB
• Silicon Manufacturer: Freescale
• Core Architecture: HC08
• Core Sub-architecture: HC08
• Silicon Core Number: MC68HC908
• Silicon Family Name: HC08Q
• Kit Contents: MC68HC908QB8, Cables, Guides
• Rohs Compliant: No
• For Use With/related Products: MC68HC908QB8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

D E M O 9 0 8 Q B 8
RS-232
An RS-232 translator provides RS-232 to TTL/CMOS logic level translation on the COM con-
nector. The COM connector is a 9-pin Dsub, right-angle connector. A ferrite bead on shield
ground provides conducted immunity protection. Communication signals TXD and RXD are
routed from the transceiver to the MCU. Hardware flow control signals RTS and CTS are
available on the logic side of U3. These signals are routed to vias located near the transceiver
(U3). RTS has been biased properly to support 2-wire RS-232 communications.
Communications signals TXD and RXD also connect to general purpose Port B signals. The
RS-232 translator should be disconnected at the COM_SEL option header if the general-
purpose I/O signals are used.
Figure 7: COM Connections
COM Connector
A standard 9-pin Dsub connector provides external connections for the ESCI port. The Dsub
shell is connected to board ground through a ferrite bead. The ferrite bead provides noise
isolation on the RS-232 connection. The figure below details the DB9 connector.
Figure 8: COM Connector
COM_SEL
The communications mode is determined by the COM_SEL jumper. This 3-pin jumper allows
the user to select between RS-232 communications and LIN communications. The figure be-
low shows the different configurations.
TXD
RXD
GND
MCU Port
PTB5/TXD
PTB4/RXD
1
2
3
4
5
6
7
8
9
RTS
CTS
NC
COM Signal
TXD OUT
RXD IN
Female DB9 connector that interfaces to the HC08 internal SCI1 serial
port via the U2 RS232 transceiver. It provides simple 2 wire asynchro-
nous serial communications without flow control. Flow control is provided
at test points on the board.
Pins 1, 4, and 6 are connected together.
14
I/O PORT
CONNECTOR
J1-5
J1-7
M A R C H
1 8 ,
2 0 0 5