EVAL-ADUC836QS AD [Analog Devices], EVAL-ADUC836QS Datasheet - Page 67

• Manufacturer Part Number: EVAL-ADUC836QS
• Description: MicroConverter, Dual 16-Bit ADCs with Embedded 62 kB Flash MCU
• Manufacturer: AD [Analog Devices]

OTHER HARDWARE CONSIDERATIONS
In-Circuit Serial Download Access
Nearly all ADuC836 designs will want to take advantage of the
in-circuit reprogrammability of the chip. This is accomplished
by a connection to the ADuC836’s UART, which requires an
external RS-232 chip for level translation if downloading code
from a PC. Basic confi guration of an RS-232 connection is illus-
trated in Figure 66 with a simple ADM3202 based circuit. If users
would rather not include an RS-232 chip onto the target board,
refer to the application note, uC006–A 4-Wire UART-to-PC Interface
available at www.analog.com/microconverter, for a simple (and
zero-cost-per-board) method of gaining in-circuit serial download
access to the ADuC836.
In addition to the basic UART connections, users will also need
a way to trigger the chip into Download mode. This is ac com -
plished via a 1 k pull-down resistor that can be jumpered onto
the
Download mode, simply connect this jumper and power-cycle the
device (or manually reset the device, if a manual reset but ton is
available), and it will be ready to receive a new pro gram serially.
With the jumper removed, the device will pow er on in Normal
mode (and run the program) whenever power is cycled or RESET
is toggled.
Note that
nal Memory Interface section) and that it is sampled as an input
only on the falling edge of RESET (i.e., at power-up or upon an
external manual reset). Note also that if any external circuitry
unintentionally pulls
it could cause the chip to enter Download mode and therefore fail
to begin user code execution as it should. To prevent this, ensure
REV. 0
pin, as shown in Figure 66. To get the ADuC836 into
is normally an output (as described in the Exter-
low during power-up or reset events,
–67–
that no external signals are capable of pull ing the
except for the external
Embedded Serial Port Debugger
From a hardware perspective, entry to Serial Port Debug mode is
identical to the serial download entry sequence described above.
In fact, both Serial Download and Serial Port Debug modes can
be thought of as essentially one mode of operation used in two
different ways.
Note that the serial port debugger is fully contained on the
ADuC836 device, (unlike ROM monitor type debuggers) and
therefore no external memory is needed to enable in-system
debug sessions.
Single-Pin Emulation Mode
Also built into the ADuC836 is a dedicated controller for sin gle-pin
in-circuit emulation (ICE) using standard production ADuC836
devices. In this mode, emulation access is gained by connection to
a single pin, the
high or low to select execution from internal or external program
memory space, as described earlier. To enable single-pin emu-
lation mode, however, users will need to pull the
through a 1 k resistor, as shown in Figure 66. The emulator
will then connect to the 2-pin header also shown in Figure 66.
To be compatible with the standard con nec tor that comes
with the single-pin emulator available from Accutron Limited
(www.accutron.com), use a 2-pin 0.1-inch pitch Friction Lock
header from Molex (www.molex.com) such as their part number
22-27-2021. Be sure to observe the polarity of this header. As
represented in Figure 66, when the Friction Lock tab is at the
right, the ground pin should be the lower of the two pins (when
viewed from the top).
pin. Normally, this pin is hard-wired either
jumper itself.
ADuC836
pin high
pin low,