ADUC834 Analog Devices, ADUC834 Datasheet - Page 67

• Manufacturer Part Number: ADUC834
• Description: Precision Analog Microcontroller: 1MIPS 8052 MCU + 62kB Flash + 16/24-Bit ADC + 12-Bit DAC
• Manufacturer: Analog Devices

Specifications of ADUC834

• Mcu Core: 8052
• Mcu Speed (mips): 1
• Sram (bytes): 2304Bytes
• Gpio Pins: 34
• Adc # Channels: 4
• Other: PWM

OTHER HARDWARE CONSIDERATIONS
In-Circuit Serial Download Access
Nearly all ADuC834 designs will want to take advantage of the
in-circuit reprogrammability of the chip. This is accomplished
by a connection to the ADuC834’s UART, which requires an
external RS-232 chip for level translation if downloading code
from a PC. Basic configuration of an RS-232 connection is
illustrated 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 ADuC834.
In addition to the basic UART connections, users will also need
a way to trigger the chip into Download mode. This is accom-
plished via a 1 kΩ pull-down resistor that can be jumpered onto
the PSEN pin, as shown in Figure 66. To get the ADuC834 into
Download mode, simply connect this jumper and power-cycle
the device (or manually reset the device, if a manual reset button
is available) and it will be ready to receive a new program serially.
With the jumper removed, the device will power-on in Normal
mode (and run the program) whenever power is cycled or RESET
is toggled.
Note that PSEN is normally an output (as described in the
External Memory Interface section) and 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 PSEN low during power-up or reset events,
it could cause the chip to enter Download Mode and therefore
fail to begin user code execution as it should. To prevent this,
ensure that no external signals are capable of pulling the PSEN
pin low, except for the external PSEN jumper itself.
REV. A
–67–
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
ADuC834 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 ADuC834 is a dedicated controller for single-
pin in-circuit emulation (ICE) using standard production ADuC834
devices. In this mode, emulation access is gained by connection
to a single pin, the EA pin. Normally, this pin is hard-wired
either high or low to select execution from internal or external
program memory space, as described earlier. To enable single-pin
emulation mode, however, users will need to pull the EA pin
high through a 1 kΩ 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 connector 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).
ADuC834