ADuC812 Evaluation Board Reference Guide
Evaluation Board Features
(2) E
VALUATION
B
OARD
F
EATURES
Power Supply:
A 9V supply is fed to the board via the 2.1mm input power socket (J4). The input connector is configured
as ‘CENTER NEGATIVE’ i.e. GND on the center pin and +9V on the outer shield. Alternatively the user
can connect a 9V battery via J9(-) and J10(+). The 9V supply is regulated via a linear voltage regulator
(U9), the 5V output being used to drive the digital side of the board directly. The 5V supply is also
filtered and then used to supply the analog side of the board.
When on, the green LED (D2) indicates that a valid 5V supply is being driven from the regulator circuit.
All analog supplies are decoupled with 10uF and 0.1uF at device supply pins. Digital supplies are
decoupled with 0.1uF at the digital supply pins.
RS232 Interface:
The ADuC812 (U1) TXD and RXD (pins 17 and 16 respectively) lines are connected to a header. The
cable which is included as part of the QuickStart Development System has a RS232 transciever at the
connecting end. This cable can be used to connect to both the evaluation board and the adaptor board.
Analog I/O Connections:
The inputs to the primary ADC are filtered with a first order (RC) anti-aliasing filter.
General Purpose prototype area
General Purpose prototype areas are provided at the top and the bottom or the evaluation board for adding
external components as required in the users application. As can be seen from the layout AVDD, AGND,
DVDD and DGND tracks are provided in this prototype area.
External Data Memory Interface:
The Evaluation board incorporates 32KBytes SRAM (U7). This external memory can be configured as a
data memory or as both code and data memory. Typically the 32Kbytes will be used as external data
memory. To configure it as switch link4 to the off position.
The MicroConverter uses a 24-bit address interface to external memory unlike a standard 8051, which
only uses 16-bit addresses. This means that the MicroConverter can address up to 16MBytes of XRAM
while the 8051 can only address 64kBytes of XRAM. This is done by multiplexing Port2 (high address
byte + page address byte) as well as Port0 (low address byte + data byte).
The ADuC812 evaluation board only contains 32kBytes of XRAM. Hence the full 24-bit address interface
to the XRAM cannot be used properly. To show this feature off we have configured the memory in two
modes using LK12 as discussed in section 1.2. The memory is addressed using 2 external latches
(74HC573, U14 and U15). U14 is used to latch the low order address on Port 0 before it multiplexes to a
data bus. U15 is used to multiplex Port2.
Note: U14 is unnecessary if the ADuC812 is addressing less than 64kBytes of XRAM.
