CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Sound Generator)

BDTY0–BDTY2: Duty level selection register (FF6FH•D0–D2)

Selects the duty ratio of the buzzer signal as shown in Table 4.12.7.3.

 

 

Table 4.12.7.3

Duty ratio setting

 

 

 

 

 

 

 

Duty ratio by buzzer frequency (Hz)

Level

BDTY2

BDTY1

BDTY0

 

4096.0

3276.8

2730.7

2340.6

 

 

 

 

 

2048.0

1638.4

1365.3

1170.3

Level 1 (Max.)

0

0

0

 

8/16

8/20

12/24

12/28

Level 2

0

0

1

 

7/16

7/20

11/24

11/28

Level 3

0

1

0

 

6/16

6/20

10/24

10/28

Level 4

0

1

1

 

5/16

5/20

9/24

9/28

Level 5

1

0

0

 

4/16

4/20

8/24

8/28

Level 6

1

0

1

 

3/16

3/20

7/24

7/28

Level 7

1

1

0

 

2/16

2/20

6/24

6/28

Level 8 (Min.)

1

1

1

 

1/16

1/20

5/24

5/28

The sound level of this buzzer can be set by selecting this duty ratio.

However, when the envelope has been set to ON (ENON = "1"), this setting becomes invalid. At initial reset, this register is set to "0".

ENRST: Envelope reset (FF6CH•D2)

Resets the envelope.

When "1" is written: Reset

When "0" is written: No operation

Reading: Always "0"

Writing "1" into ENRST resets envelope and the duty ratio becomes maximum. If an envelope has not been added (ENON = "0") and if no buzzer signal is being output, the reset becomes invalid. Writing "0" is also invalid.

This bit is dedicated for writing, and is always "0" for reading.

ENON: Envelope ON/OFF control register (FF6CH•D1)

Controls the addition of an envelope onto the buzzer signal.

When "1" is written: ON

When "0" is written: OFF

Reading: Valid

Writing "1" into the ENON causes an envelope to be added during buzzer signal output. When a "0" has been written, an envelope is not added.

At initial reset, this register is set to "0".

ENRTM: Envelope releasing time selection register (FF6CH•D3)

Selects the envelope releasing time that is added to the buzzer signal.

When "1" is written: 1.0 sec (125 msec ⋅ 7 = 875 msec)

When "0" is written: 0.5 sec (62.5 msec ⋅ 7 = 437.5 msec)

Reading: Valid

The releasing time of the digital envelope is determined by the time for converting the duty ratio.

When "1" has been written in ENRTM, it becomes 125 msec (8 Hz) units and when "0" has been written, it becomes 62.5 msec (16 Hz) units.

At initial reset, this register is set to "0".

S1C63558 TECHNICAL MANUAL

EPSON

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