|
Basic Information
Question 1
What's form of interface, serial or parallel, is used for data transfer in the HT16XX Series, and how many I/O lines are required?
Answer
The HT16XX series of devices is designed to function with a serial interface, which has both a four and seven I/O line type.
For the HT1620-HT1626 devices, a four-line interface is provided which consists of the following pins, CS, RD, WR and DATA.
The HT1647 device has a seven-line interface, consisting of pins CS, RD,
VR, and DB0-DB3. Data is transferred along four lines which provides faster data transfer rates.
Question 2
How long does it take the HT16XX series of devices to refresh? Also how long does it take to refresh all frames?
Answer
The typical refresh frequency of the HT16XX devices is 64Hz. The refresh time is 1/64 sec.
Question 3
What's the LCD pixel capacity for the HT16XX series of devices?
Answer
The following table shows the pixel capacity of the devices in the HT16XX range.
| Product No |
Pixels |
| HT1621 |
32*4 (128 pixels) |
| HT1622 |
32*8 (256 pixels) |
| HT1623 |
48*8 (384 pixels) |
| HT1625 |
64*8 (512 pixels) |
| HT1647 |
64*16 (1024 pixels) |
| HT1650 |
64*32 (2048 pixels) |
| HT1660 |
96*32 (3072 pixels) |
| HT1670 |
128*32 (4096 pixels) |
Functional Description
Question 1
What's the purpose of the built-in display RAM in the HT16XX series? Answer
The built-in display RAM of the HT16XX series of devices is directly related to the pixels. The RAM is utilised to the store the LCD screen data. After the MCU has read the data that is to be displayed, the HT16XX device will display the data automatically on the LCD. There is no need to send any new data except for the frame change. In this way the loading can be reduced.
Question 2
Why can I not get the Timer output from the /IRQ pin of the HT1621?
Answer
The /IRQ pin output can be selected as WDT or Timer output via commands. If Timer output is selected, then the Timer waveform will appear on the
/IRQ pin. If WDT is selected, the /IRQ output will change from high to low when the WDT overflows. For example, if 1Hz Timer signal is on, the
/IRQ pin is required and commands are given as follows:
CLR TIMER
TIMER EN ;connect TIMER output to
/IRQ pin
F1
;choose 1Hz TIMER output
IRQ EN
If there's still no Timer waveform on the /IRQ pin, check if the WDT EN or IRQ DIS command is mistakenly given. Note that a pull-high resistor on the /IRQ line is required.
Application Description
Question 1
When using the HT1650/1660/1670 LCD Driver, why is the illumination of some pixels uneven?
Answer
The problem of uneven illumination of LCD pixels can be caused by insufficient drive current from the LCD driver, this can be resolved in 2 ways:
-
By using LCD panels with a COM-SEG capacitance value of less than 10pf, reducing the size of the pixels and choosing higher quality displays are all measures which can be used to increase impedance and reduce the loading effects of the application circuit.
-
Increase the current drive of the HT1650/1660/1670
-
Increase VLCD, which will increase the
Vrms-on and Vrms-off window, which will increase the light/dark contrast.
-
Choose a large Bias Current.
-
Choosing a suitable resistor value (about 1K) to be placed between the pins VDD -T1, T1-T2, T2-T3, T3-T4, T4-T000 and T000-VSS etc and choosing a suitable capacitance value (about 0.1uF) to be placed between the pins T1-VSS andT4-VSS will reduce the output impedance and increase the drive current capability of the device.
Question 2
How can the HT1670 be connected to a 105 X 65 LCD display?
Answer
The HT1670 was designed for a 128 X 32 display. As the device cannot expand its com and seg outputs it can only be used with 128 X 32 displays.
Question 3
Is the method of using the HT49R30A-1 Bank 1 Data Memory and the Bank 0 Data Memory the same? Are there any special points to note when using?
Answer
When interrogating Bank 1 in the HT49R30A-1, the Bank Pointer register, BP, should first be set to 1. Then the MP1/IAR1 memory pointer indirect addressing register pair should be used to read and write to the Data Memory. Note that for different duty values the Data Memory address space is also different. For 1/2 and 1/3 duty, the Data Memory address space is from 40H~52H. For 1/4 duty the Data Memory space is from 40~51H. Also note that each Data Memory address only uses the lowest four bits, namely bits 0~3, which can be read and written to.
Points to Note
Question 1
Can the HT16XX ram be used as memory if the MCU RAM is insufficient? How can this be achieved and is there anything special that should be noted?
Answer
Yes, this is possible. However, it must be noted that the HT16XX ram can be retrieved as common RAM which will be displayed on the LCD, so it is important to select the hidden RAM if it is to be used as common RAM.
Question 2
In the HT1621 datasheet, in the section for the HT1621B-48 LQFP-A pin assignments, is the order of the SEG number on Pin 20 and Pin 21 correct?
Answer
The SEG number on Pin 20 and Pin 21 is correct. Pin 20 is SEG 27 and Pin 21 is SEG 28. This way of numbering is used for convenience in wiring between the lead frame and the DICE.
Others
Question 1
What applications are applicable for the HT16XX series of devices?
Answer
The HT16XX range of devices are applicable for use on applications such as telephones, toys, games and other consumer products.
Question 2
Is the interface specification of HT16XX series of devices a standard one?
Answer
The HT16XX series of devices is representative of other devices on the market, for this reason the interface could be considered as a standard specification.
|
