May
2006, Issue 190
Mobile
Phone Book
M16C/62P-Based
Data Backup System
Renesas M16C 2005 Honorable Mention
HARDWARE
& SOFTWARE
The
Mobile Phone Book uses all of the M16C/62P demonstration
board’s resources. I built an expansion board for the
RS-232 channel communication and the SIM smart card
interface (see Photo 2, p. 14). The RS-232 interface
is built around the MAX232 level shifter. I wired it
in accordance with the manufacturer’s specifications.
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(Click
here to enlarge)
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Photo
2—The expansion board features a SIM connector,
serial capability, and a header connector. The hardware
for dealing with the SIM smart card is simple because
all the complexity has been moved to the software
side. |
The
SIM smart card interface is a special socket for interfacing
the SIM to the M16C/62P’s UART2 (see Figure 2, p. 15).
You can implement the interface with just two microcontroller
pins. One pin handles the RST signal. The other pin
drives the I/O signal. In this minimal configuration,
the VCC, GND, and CLK signals are always active.
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(Click
here to enlarge)
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Figure
2—I connected the expansion board to the Renesas
M16C/62P demonstration board with off-the-shelf
components. Thanks to the 10-kW pull-up resistor,
I converted a full-duplex protocol to half duplex. |
The
I/O signal can be driven to configure the UART2 as an
asynchronous serial protocol using 1 stop bit, 8 data
bits (least significant bit first), even parity, and
2 stop bits, running at 9,600 bps when the external
clock applied to the SIM card through its clock signal
CLK is 3.57 MHz. For simplicity, the error detection
and character repetition procedure isn’t implemented.
UART2
is a full-duplex peripheral with separated reception
(TxR2) and transmission (TxD2) lines. On the other,
the SIM works as a half-duplex device with just one
I/O line for I/O data. Therefore, you need a hardware
translation mechanism. Simply join the TxD2 and RxD2
signals through a 10-kW pull-up resistor. This will
enable the UART2 and the SIM to talk to each other via
a standard asynchronous protocol.
The
software is the key to this project. I developed all
of the software in a modular way in C language, so maintaining
and improving the software is simple. Table
1 includes brief descriptions of each module. Figure
3 shows the module hierarchy.
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(Click
here to enlarge)
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Figure
3—The module hierarchy in the software design is
fairly simple. There are different layers of complexity.
Each microcontroller peripheral has its own driver
in a separate source file. |
