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R0P7727TH003TRKE General Information Manual
5.5 Sound Generator
5.5.1 Block Description
Figure 5.8 shows the sound generator control block. As shown in Figure 5.8, this control block contains an
SH7727 internal serial I/O controller (SIOF), and an A/D-D/A converter for digital audio (AK4550 from Asahi
Kasei) so that sound can be output to headphones connected to an output mini-jack (CN9) or it can be input to
earphones connected to an I/O mini-jack (CN8). In addition, headphone output takes place with the quality of
stereo output while earphone I/O takes place with the quality of monaural I/O that uses only the Rch.
This control block is connected to an electronic volume so that sound output volume can be controlled. The
electronic volume is controlled by the power supply controller.
Controller."
The SH7727 port (PTK1) can be controlled to change the master clock (SIOMCLK, MCLK) for the SH7727
internal SIOF controller and AK4550, resulting in the change of the sound generator.
The control method is shown below.
"Low" output from PTK1: The master clock is 2.028Mhz and the sampling rate is 8KHz.
"High" output from PTK1: The master clock is 11.2896MHz and the sampling rate is 44.1KHz.
Figure 5.9 shows an AK4550 power-on sequence. The SH7727 port (PKT0) is connected to the AK4500
power-down pin (PWAD, PWDA) so that AK4500 power-on control can take place. When T-Engine is turned
on or the master clock is changed, the power-on sequence must be executed.
The control method is shown below.
Low-level output takes place from SH7727 PTK0 to produce low-level input to the PWAD and PWDA pins of the
AK4550 causing a power-down state. This duration is maintained for 150ns or more, then high-level output
takes place from SH7727 PKT0 to produce high-level input to the PWAD and PWDA pins of the AK4550,
causing a normal operating state.
T-Engine has the following characteristics for microphone input and headphone output:
- Microphone input
Impedance: 2.2KΩ
Sensitivity: -51dB/Pa
- Headphone output
Impedance: 32Ω
For more details, refer to the pertinent Asahi Kasei AK4550 Manual.
Asahi Kasei Homepage:
http://www.asahi-kasei.co.jp/asahi/en/index.html
For details, refer to 6, "Power Supply
34
Functional Blocks
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