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HANDS-ON MICROCONTROLLERS
38
Figure 2. A LED blinker using the R8C/13 – no crystal necessary!
specifically the R8C/13) in the coming issues of Elektor
Electronics. We have planned articles on how to use
the software and some typical application examples.
Naturally, a user competition also forms part of the picture.
Here we’d like to whet your appetite a bit by
describing the principal features of this small but elegant
microcontroller.
The core
The CPU achieves a processing performance of 8 MIPS
at a 20-MHz clock frequency and boasts 89 native
instructions. Of that number, 20 are single-cycle instructions,
and three quarters of the instructions execute in five
clock cycles on average. Mathematical operations, such
Figure 3. The model E8 hardware debugger (optionally available) has a true
real-time mode.
as a 16-bit by 16-bit multiplication, are completed in
250 ns, and division of a 32-bit quotient with a 16-bit
dividend takes 1248 µs. The instruction set includes an
RMPA instruction (calculate sum of products), which can
be used to compute digital filter algorithms.
The instruction set has special space-saving instructions
that allow short data words (with a length of 1, 2, 4 or
8 bits) to be stored in one, two or three bytes along with
the instruction opcode. The same capability is also available
for addresses. The Compare function has been
extended to enable MOV instructions to load data
depending on flag states without requiring a prior comparison.
The peripherals
The R8C/13 has three 8-bit timers, one 16-bit timer, a
watchdog timer, a very fast 10-bit A/D converter with
twelve inputs and a conversion time of 3.3 µs, two UARTs
(one of which can also be used synchronously), flash program
memory, flash data memory in the form of a virtual
EEPROM, SRAM, eight I/O lines with a rated current of
20 mA (for directly driving devices such as LEDs), an
undervoltage detector, two integrated oscillators (calibratable
125-kHz and 8-MHz ring oscillators), and a crystal
oscillator. The reset peripheral is also integrated using a
5-bit counter.
As with other Renesas microcontrollers, the current consumption
is very low. It is 7.9 mA at 5 V and 16 MHz,
dropping to 4 mA at 5 V for operation using the 8-MHz
ring oscillator or 470 µA at 5 V for operation using the
124-kHz ring oscillator. In Stop mode the current consumption
is only 0.7 µA.
A particularly attractive feature for model builders is the
IC’s ability to boot using the low-speed oscillator. As can
be seen from Figure 2, all you need to implement a minimal
application (such as a LED blinker) is a programmed
R8C/13 and a resistor.
The debug interface
The R8C family has an integrated debug interface with
asynchronous and synchronous serial interfaces for easy,
inexpensive debugging. The asynchronous mode is especially
easy to use, because all you have to add is an
RS232 level converter. For debugging you will need the
KD30 debugger program, which first flashes a monitor
program into the R8C and then starts it automatically.
The debug interface is also suitable for downloading a
fully developed program in the flash ROM of the microcontroller.
You can use the Flashstart or FDT program for
this purpose.
These programs, as well as all other software mentioned
here, are available free of charge from
www.renesas.com or www.m16c.de. Naturally, the programs
are also located on the software CD-ROM available
from Readers Services.
The tools
Renesas supports developing small, medium-sized and
large projects using corresponding software. In that
regard, a distinction must be made between three levels,
which differ in cost, scope and capability. At the first
level, the potential user can manage entirely without purchased
software. There is even a GNU C compiler available
now for the M16C family.
elektor electronics - 1/2006