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Basic Information
Question 1
How many different body types are available for the HT36 series? How can the most suitable one be selected?
Answer
It is recommended that the HT36A4 is used if fewer melodies and less functions are required. Otherwise, it is recommended that the HT36B0 is used for more advanced applications.
Question2
What is the system frequency tolerance if an RC oscillator is used as the system clock?
Answer
If the RC oscillator is selected, due to tolerances in the device processing, a nominal
±20% frequency tolerance from lot to lot is expected. Assuming that the external resistor has a
±5% tolerance, then the overall frequency tolerance would be ±25%.
The above specified tolerance is provided as a reference only and is not guaranteed. For applications where a more precise frequency source is required it is recommended that either a resonator or crystal frequency source is used.
Question3
When the HT36B4 is operating in the RC mode, is the frequency output which is seen on the frequency monitoring output pin, OSC2, equal to 1/8 or 1/4.
Answer
Because the frequency (FOSC2) monitoring output pin, OSC2, has a frequency of 1/4 the system frequency FSYS, therefore FOSC2 = FSYS/4. Because the system frequency, FSYS, of the HT36, is 1/2 of the oscillator frequency, FOSC, then FYS = FOSC/2. Therefore FOSC2 = FYS/4 = FOSC/8.
Functional Description
Question 1
What is the difference between the HT36A0 and HT36A2 device, both of which use a 1M-bit ROM?
Answer
The HT36A2 is a cost down version of the HT36A0 device. With the same ROM size, however, the HT36A0 is a 16 channel device while the HT36A2 is only an 8 channel device. The HT36A0 also has a stereo output while the HT36A2 has a mono output. The HT36A2 also has 20 I/Os while the HT36A0's has 28I/Os.
Question 2
What is the function of the WDT?
Answer
The WDT is designed to monitor the MCU software and hardware operations. Users should employ the CLEAR WDT
(CLR WDT or CLR WDT1 and CLR WDT2 ) instructions should any abnormal operation or malfunction happens when a WDT overflow would occur which will then reset the MCU to resume normal operation. The WDT monitoring effects mainly depend on the software program design.
Question 3
For the HT36A MCU device, how can the program jump between different banks?
Answer
The Program Memory in the HT36A series of MCUs has each 8K words of memory defined as one Bank. If the application data or the program is especially large, it is possible to store it in other banks. For data or code that is to be stored in Banks other than Bank 0, it is necessary to place this into a different .asm file. For example to place data or code into Bank 1, it should be placed into a file with the name user1.asm. Data or code placed into other banks can be similarly located using different .asm files with the name userX.asm, where X is the Bank number. However it must be noted that most of the userX.asm files will not be available for use as they will already be used by the waveforms. Every Bank contains 32 pages of data, with every page having a capacity of 256 words. When the program wants to jump between Banks it can only jump to address 0 of the indicated page. However if data is to be read, it can be read from any address. The following method can be used to achieve this:
indicate the fileno parameter (this is also the Bank number)
indicate the pageno parameter
indicate the address parameter（If it is a program jump to a different bank, then this is not required）
call getextdata
In this way the program will jump to the indicated bank and page at address 0 or to the indicated address in the indicated bank if data is to be read.
To return, use the jmp backpage0 instructions.
Note that the last page in each bank（i.e. page 31）can only contain data, it is not allowed to store program instructions in this area.
Question 4
When using the HT37P00 with battery power, how is it possible to eliminate the Sound Bursts problem?
Answer
In order to eliminate the Sound Bursts problem, the following steps are recommended:
Turn on: audio signal standby(1/2VDD)->enable amplifier->wait tR for amplifier ready->audio output
Turn off: audio signal finished->disable amplifier->wait tR for amplifier->audio signal off
Application Description
Question 1
Why are their changes in frequency when the volume is adjusted during sound play?
Answer
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When batteries are used for an extended period their input resistance increases and output voltage will reduce in magnitude. This may cause some variations in the operation frequency of the oscillation circuit within the device. Changing the batteries will of course resolve this problem.
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The large AC currents required by the speaker driver circuits may also cause variations in the power supply. Connecting a suitable electrolytic capacitor, such as 47µf, between the power supply lines will help to resolve this problem.
Question 2
Is it normal for the temperature of the speaker driver transistor to be high?
Answer
Driving a speaker directly using a transistor is known as a class-A amplifier circuit. There should be no problem having the transistor run at a higher temperature. However to avoid this situation, it might be useful to investigate using the HT82V733 amplifier as an alternative means of driving the speakers.
Question 3
If the power environment of the application circuitry is not of a high standard, will this affect the sound quality of the IC?
Answer
If the power contains noise, the sound quality will be influenced by such noise, which will be transferred from the IC power to the sound output port. One method of reducing this IC noise is to connect a 47ohm resistor between VDD of the IC and the power line and then to connect a 10uf capacitor between the VDD pin and VSS.
Question 4
What tools are required to record a section of music from a CD to an IC? Answer
There are two ways to record sounds from a CD onto an IC:
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Place a CD into a traditional audio CD player. Play and record the sound into the PC by using a standard PC SoundBlaster or compatible card. Software such as the standard recording program within Windows or other shareware or professional recording programs are all suitable. A file quality of 8KHz and 16-bit is recommended.
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Audio CD can be transferred to 44.KHz and 16-bit wav files from the PC. Use the program to transfer the files to a lower sampling rate suitable for the project.
Question 5
If the RC oscillator is selected as the system clock, what are the purposes of the external resistor and capacitor? Can the capacitor be omitted?
Answer
The external resistor on the OSC1 pin is used to generate bias to control the internal RC charge and discharge. The frequency of the RC oscillator is determined by the value of this external resistor. The recommended 470pF external capacitor, which is connected to the OSC1 pin, is added to avoid cross-talk to the OSC2 line. The OSC2 pin is provided to supply an output frequency of 1/4 system frequency. However, if this 1/4 system frequency output, OSC2, is not utilized, the external capacitor on OSC1 pin can be omitted.
Question 6
When a polyphone IC is working in the external MCU control mode, when the external MCU is transmitting instructions what are the special points to note?
Answer
When the polyphone IC is working in the external MCU control mode, if the time between power-on and the receipt of the first instruction, is less than 400ms, then this may result in the loss of this instruction. For this reason, in general, before the external MCU transmits an instruction, a delay of greater than 400ms should be allowed for.
Points to Note
Question 1
What precautions should I take in designing the MCU Reset and
Oscillator circuit?
Answer
Please refer to the "HA0075E"
in the Application Notes
section of our company web site.
Question 2
Are there any special points to note for pin OSC2 when using the RC mode in the HT37P00?
Answer
This output is different to that of most other devices. For most devices pin OSC2 will output a frequency of Fsys/4, however in this device the frequency on OSC2 will be Fsys/8, which can be used for external circuit synchronisation.
Others
Question 1
Is the reason why the HT36 series has a higher sound quality due to a higher quality DAC?
Answer
Synthesized music by a standard Voice MCU is usually too discordant and lacks the vividness and quality of natural musical instruments. The reason why the HT36 series has an enhanced sound quality is not just due to a better DAC but also because wave-table technology is used which provides a far higher sound quality than that of a standard voice MCU.
Question 2
For Holtek's MCUs, is there any way to reset the stack pointer
other than by a chip RESET?
Answer
The stack pointer is affected by the execution of interrupts as
well as by any subroutine calls which occur in the application
program. In addition, any return instructions will also affect the
stack pointer. However, it is not possible for the user to
directly reset the stack pointer by any means other than the chip
RESET.
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