User’s Manual
M68HC12A4EVB Evaluation Board — Rev. 1
30
Configuration and Setup
MOTOROLA
Configuration and Setup
Standard, commercially available cables may be used in most cases. Note that
the EVB uses only three of the RS-232C signals.
Table 2-1
lists these signals
and their pin assignments.
The EVB’s RS-232C connectors, J2 (default) and J3 (unpopulated footprint),
are wired as data circuit-terminating equipment (DCE) and employ 9-pin
subminiature D (DB-9) receptacles. The equivalent 3-pin headers, J1 and J4,
serve the same purposes and may be used for customized cabling.
Most terminal devices — whether dumb terminals or the serial ports on host
computers — are wired as data terminal equipment (DTE) and employ 9- or
25-pin subminiature D (DB-9 or DB-25) plugs. In these cases, normal
straight-through cabling is used between the EVB and the terminal. Adapters
are readily available for connecting 9-pin cables to 25-pin terminal connectors.
If the terminal device is wired as DCE, the RXD and TXD lines must be
cross-connected, as shown in
Table 2-1
. Commercial null modem adapter
cables are available for this purpose.
Optionally, the MCU’s background debug mode (BDM) interface can serve as
the user interface. This setup makes both of the SCI ports available for user
applications. Additional hardware and software are required. For more
information, refer to the documentation for the background debug development
tool being used, such as Motorola’s serial debug interface.
NOTE:
D-Bug12 does not use the BDM interface.
Table 2-1. RS-232C Interface Cabling
EVB Pins, Always DCE
DTE Signal
Terminal Pins
J3
(1)
/ J2
(2)
DB-9
Receptacle
J4
(1)
/ J1
(2)
3-Pin
Header
DTE
(3)
Plug
DCE
(4)
Receptacle
DB-9
DB-25
DB-9
DB-25
2
2
Receive data (RXD)
2
2
3
3
3
3
Transmit data (TXD)
3
3
2
2
5
1
Ground (GND)
5
7
5
7
(1)
Factory default. Terminal interface uses SCI0.
(2)
Optional. Terminal interface uses SCI1. Hardware modifications are required. For details, refer to
4.5 Terminal
Interface
.
(3)
Normal (DCE-to-DTE) cable connections
(4)
Null modem (DCE-to-DCE) cable connections
F
re
e
sc
a
le
S
e
m
ic
o
n
d
u
c
to
r,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
c
.
..
AR
CH
IVE
D B
Y F
RE
ES
CA
LE
SE
MI
CO
ND
UC
TO
R,
IN
C.