HC05A24EM USER’S MANUAL
MOTOROLA
2-3
2
2.1.3
Clock Source Select Header (P6)
Jumper header P6 determines the source of the clock signal. The dia-
gram below shows the factory configuration: the fabricated jumper
between pins 2 and 3 selects the A24EM canned oscillator clock source.
Alternatively, you may use a clock source originating from the control
board. To do so, reposition the P6 jumper between pins 1 and 2, then use
the MMDS05 OSC command to select a frequency.
2.1.4
Clock Divider Header (P9)
Jumper header P9 determines which internal clock divider of the MCU
to use on power up or reset. The diagram below shows the factory con-
figuration: the fabricated jumper between pins 1 and 2 selects the divide
by two MCU clock divider. This is the correct configuration for a 4 MHz
clock source. If a 16 MHz clock source is used. The user must remove
the fabricated jumper between pins 1 and 2 to select the divide by eight
MCU clock divider.
1
2
3
P6
XTAL
MMDS05
FABRICATED
JUMPER
1
2
P9
OPEN = OSC/8
FABRICATED
JUMPER
INTERNAL
CLOCK DIVIDER
CLOSE = OSC/2
