M38049F8HKP datasheet(261/387 Pages) RENESAS

261 / 387 page

2-137

APPLICATION

2.8 D/A converter

Rev.1.00 Jan 14, 2005

REJ09B0212-0100Z

3804 Group (Spec.H)

When the registers are set as shown in Figure 2.8.7, the speaker output volume is modulated by the

D/A output value. Figure 2.8.8 shows the control procedure.

Fig. 2.8.8 Control procedure

RESET

Initialization

SEI

CLT (Note 1)

CLD (Note 2)

ICON1

P3D

ADCON

T12XCSS

PREX

WORK flag (Note 3)

IREQ1

ICON1

DA1

CLI

2 – 1

D616 – 1

Main processing

Value of WORK flag ?

“1”

“0”

RTI

(address 003E16), bit4

(address 000716), bit0

(address 003416)

(address 002316)

(address 000E16)

(address 002416)

(address 002516)

(address 003C16), bit4

(address 003E16), bit4

(address 003616)

(address 002316)

Timer X interrupt process routine

Pop registers

X1XXXXXX2

•All interrupts disabled

•Timer X interrupt disabled

•Set port P30 to input mode

•DA1 output enabled

•Timer Y: Timer mode, Timer X count: Stop

•Timer X count source: f(XIN)/16

•Set “division ratio – 1” to Prescaler X

•Set “division ratio – 1” to Timer X

•Timer X interrupt request bit cleared

•Timer X interrupt: Enabled

•D/A converter start

•All interrupts enabled

•Timer X count start

Notes 1: When using Index X mode flag

2: When using Decimal mode flag

3: The WORK flag is a user flag for work. When this flag is “1

”, a value other than Vss is output from the DA output pin.

When this flag is “0”, Vss is output from the DA output pin.

•Push registers used in interrupt process routine

•Pop registers pushed to stack

q x: This bit is not used here. Set it to “0” or “1” arbitrarily.

XX001XXX2

Set output value (volume)

XX000XXX2

Push registers to stack

Set value except Vss to DA1 conversion

Set “0” to WORK flag.

Set value of Vss to DA1 conversion register.

Set “1” to WORK flag.

✻ Decide an D/A value from several times of D/A conversion results.

0011XXXX2

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