D E M O 9 0 8 L B 8
M A R C H 2 4 , 2 0 0 5
13
Bus operating frequency is one-fourth (¼) the selected timing source. The figure below shows
the different option settings.
Figure 7: OSC_EN Option Header
ON
Enables 9.8304 MHz Input to MCU on OSC1
1
2
OFF
Disables 9.8304 MHz Input to MCU on OSC1
OPAMP_EN
The OPAMP_EN option header connects a photocell to the OP AMP/Comparator input on the
MCU. This option header also enables the feedback loop on the op amp. The table below de-
scribes the setup for the OPAMP_EN option header. Refer to the MC68HC908LB8 manual for
details on the operation of the OP AMP/Comparator. The table below shows the OPAMP_EN
option header.
Table 3: OPAMP_EN Option settings
Jumper
ON
OFF
MCU PORT
OPAMP_EN-1
Enable RZ1
Disable RZ1
PTB5 (U1-11)
OPAMP_EN-2
Enable Feedback
Disable Feedback
PTB6 (U1012)
USER OPTIONS
The DEMO908LB8 provides 2 push-button switches, 2 LED indicators, a potentiometer, and a
photocell circuit for use in application development. The photocell is connected to a gain stage
amplifier internal to the MCU. The USER_EN option header allows each option to be enabled
or disabled individually. To enable a user option, simply install the appropriate jumper. Re-
move the jumper to disable an option. The table below which jumper controls each user func-
tion. The table also shows the signal assigned to each user function.
NOTE:
To enter monitor mode, jumper USER-5 must be removed. Otherwise,
attempts to enter monitor mode will fail.
Table 4: USER_EN Option Settings
Jumper
On
Off
MCU PORT
User-1
Enable SW1
Disable SW1
PTB3 (U1-9)
User-2
Enable SW2
Disable SW2
PTB4 (U1-10)
User-3
Enable LED1
Disable LED1
PTA2 (U1-16)
User-4
Enable LED2
Disable LED2
PTA3 (U1-17)
User-5
Enable POT
Disable POT
PTA1 (U1-15)
OPAMP_EN - 1
Enable SENSOR
Disable SENSOR
PTB5 (U1-11)
OPAMP_EN - 2
Enable Feedback
Disable Feedback
PTB6 (U1-12)
NOTE:
User-5
must
be disabled when attempting monitor mode entry.
