ML63295A User’s Manual
Chapter 12
Melody Driver (MELODY)
12 – 4
bit 1, 0: MBM1, MBM0
These bits select the buzzer output mode.
Output of two types of intermittent tones, a single tone or a continuous tone can be selected.
At system reset, MBM1 and MBM0 are cleared to “0”, selecting output of intermittent tone 1.
Buzzer output mode
Waveform
Intermittent tone 1
Intermittent tone waveform synchronized to 8 Hz output of time
base counter
Intermittent tone 2
Intermittent tone waveform synchronized to the logical AND of
8 Hz signal output and a “L” level of 1 Hz signal output of the
time base counter
Single tone
Single tone waveform beginning when EMBD is set to “1” until
second falling edge of 32 Hz output of time base counter
Continuous tone
Continuous tone waveform that is constant while EMBD is “1”
Figure 12-2 shows the output waveforms of the melody driver output pins.
Figure 12-2
Output Waveforms of Melody Driver Output Pins
12.4
Melody Circuit Operation
After the melody tempo is set in the tempo register (TEMP), execution of an MSA instruction will start operation
of the melody circuit.
The melody circuit outputs melody data while automatically reading melody data in ROM (program memory) as
specified by an MSA instruction.
When the last melody data is read (END bit is “1”), the melody circuit
generates a melody end interrupt request.
At this time, if an MSA instruction is executed, after the last melody
data is output, melody output will continue from the melody data specified by the MSA instruction.
If an MSA
instruction is not executed, the melody output will stop after the last melody data is output.
MSF (bit 3 of MDCON) is a flag indicating the melody output status. When MSF is “1”, the melody is being
output, and when “0”, the melody is stopped.
Setting MSF to “0” during melody output will forcibly stop the
melody output.
If it is required to stop melody output forcibly, describe the program according to the “Note” on
page 12-3.
If forcibly stopped, the melody output cannot be restarted at the address at which it was stopped.
Cycle specified by tone code
MD output
MDB output
Output state
No output state
Output state