Keil MCB251, User Manual

Page: 15 / 60

MCB251 Evaluation Board User’s Guide 9
Configuration Jumpers
The following sections describe each of the configuration jumpers of the
MCB251 board.
NMI: Default ON
The NMI configuration jumper selects whether or not the INT push-button is
connected to the NMI pin on the Temic 251G1 microcontroller. If NMI is OFF,
the INT push-button is connected to the NMI pin on the Temic 251G1. If NMI
is ON, pin 34 is connected to GND.
INT1: Default ON
The INT1 configuration jumper selects whether or not the INT push-button is
connected to port pin 3.3 on the microcontroller. If the INT1 switch is ON, the
INT push-button is connected to port 3.3. If INT1 is OFF, the INT push-button
is not connected to port 3.3.
PAGE / NONP: Default NONP
These nine configuration jumpers select whether the MCB251 board operates in
page mode or non-page mode. When these jumpers are in the PAGE position,
the address/data bus is configured for 251/151 page mode. When the jumpers
are in the NONP position, the standard 8051 bus or 251/151 non-page mode is
selected.
In page mode the data and upper address byte are multiplexed on port 2 (this
mode is available only on the 251/151). In non-page mode the data and lower
address byte are multiplexed on port 0 (this mode is available on the 251, 151,
and 8051). This jumper setting should be set to coincide with the CPU CONFIG
BYTE settings. Refer to the 251 or 151 Microcontroller User’s Manual for
more information about these modes.