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Decrement grade register (sgdr), Tone count register (sgtr) – FUJITSU MB91460 SERIES FR60 User Manual

Page 884

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Chapter 42 Sound Generator

3.Registers

value represents the amplitude of the sound. The register value is reloaded into the PWM pulse
generator at the end of every tone cycle.

When the DEC bit is "1" and the Decrement counter reaches its reload value, this register value is
decremented by 1(one). And when the register value reaches "00", further decrements are not
performed. However the sound generator continues its operation until the ST bit is cleared.

The following figure shows the relationship between the register value and the PWM pulse.

When the register value is set to "FF", the PWM signal is always "1".

Decrement Grade Register (SGDR)

The Decrement Grade register stores the reload value for the Decrement counter. They are
prepared to automatically decrement the stored value in the Amplitude Data register.

When the DEC bit is "1" and the Decrement counter counts the number of tone pulses up to the
reload value, the stored value in the Amplitude Data register is decremented by 1 (one) at the
end of the tone cycle.

This operation realizes automatic decrement of the sound with fewer number of CPU
interventions.

It should be noted that the number of the tone pulses specified by this register equals to "register
value +1". When the Decrement Grade register is set to "00", the decrement operation is
performed every tone cycle.

Tone Count Register (SGTR)

The Tone Count register stores the reload value for the Tone Pulse counter. The Tone Pulse
counter accumulate the number of tone pulses (or number of decrement operations) and when it

One PWM Cycle

00h

Register value

One input clock cycles

80h

256 input clock cycles

129 input clock cycles

255 input clock cycles

FEh

FFh

256 input clock cycles

7

6

5

4

3

2

1

0

SGDR

Bit number

Read/write

Initial value

Decrement Grade register

Address: 00019F

H

(R/W)

(R/W)

(R/W)

(R/W)

(R/W)

(R/W)

(R/W)

(R/W)

(X)

(X)

(X)

(X)

(X)

(X)

(X)

(X)

D7

D6

D5

D4

D3

D2

D1

D0

15

14

13

12

11

10

9

8

SGTR

(R/W)

(R/W)

(R/W)

(R/W)

(R/W)

(R/W)

(X)

(X)

(X)

(X)

(X)

(X)

Bit number

Read/write

Initial value

Tone Count register

Address: 00019E

H

D7

D6

D5

D4

D3

D2

D1

D0

(R/W)

(R/W)

(X)

(X)