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D E M O 9 0 8 L B 8
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
1
2
OFF
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
OPAMP_EN-1
OPAMP_EN-2
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
User-1
User-2
User-3
User-4
User-5
OPAMP_EN - 1
OPAMP_EN - 2
NOTE: User-5 must be disabled when attempting monitor mode entry.
Enables 9.8304 MHz Input to MCU on OSC1
Disables 9.8304 MHz Input to MCU on OSC1
ON
Enable RZ1
Enable Feedback
On
Enable SW1
Enable SW2
Enable LED1
Enable LED2
Enable POT
Enable SENSOR
Enable Feedback
OFF
MCU PORT
Disable RZ1
PTB5 (U1-11)
Disable Feedback
PTB6 (U1012)
Off
MCU PORT
Disable SW1
PTB3 (U1-9)
Disable SW2
PTB4 (U1-10)
Disable LED1
PTA2 (U1-16)
Disable LED2
PTA3 (U1-17)
Disable POT
PTA1 (U1-15)
Disable SENSOR
PTB5 (U1-11)
Disable Feedback
PTB6 (U1-12)
13
M A R C H
2 4 ,
2 0 0 5
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