Analog Devices MICROCONVERTER ADUC812 Reference Manual page 5

Configuring the memory as a code memory might be useful in some applications. It is necessary for the
Keil Monitor-51 which requires von-Neumann wired code and XData memory. To configure this memory
as a data and code memory switch link 4 to the on position.
Note: If using the external data memory as both external program memory and external data
memory make sure that there is no external program memory in the program memory socket
provided, (U12). Switching on LK4 with a an external program memory inserted in U12 will cause
both U7 and U12 to be enabled together and will cause confliction on the data bus.
External Program Memory Socket:
An external program memory socket is available on the ADuC812 evaluation board. This allows the user
to easily connect in an external program memory.
Note: If using an external program meory at U12 make sure that LK4 is switched to the off position
as described above.
Crystal Circuit:
The board is fitted with a 11.0592MHz crystal. This crystal is connected between the XTAL1 and XTAL2
pins. 2 X 33pF surface mount caps are used to connect XTAL1 and XTAL2 to ground.
External Power on Reset Chip (ADM809)
An external power on reset chip is used to drive the RESET pin on the ADuC812. Because we want a
push button switch available to the user an active low Power on Reset chip (ADM809) is used with
5(6(7 output inverted (using a PNP BJT) before being connected to the RESET pin of the
MicroConverter.
Alternatively, if a push button switch is not required, the RESET output of an active high power
on reset chip (e.g. ADM810) can be used to directly drive the RESET pin of the ADuC812.
Reset/,17 Push Buttons:
ADuC812 Evaluation Board Reference Guide
POWER SUPPLY
1k
POR
(ACTIVE LO W)
OPTI ONAL
MANUAL RESET
PUSH-BUTTON
POWER SUPPLY
POR
(ACTIVE HIGH)
A Du C8 12
20
DV
34
DD
48
RESET
15
ADuC812
20
DV
34
DD
48
15 RESET
Evaluation Board Features