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Design of 16 dot matrix LED electronic display screen based on MCS-5 1
1. Background introduction
1. 1 LED and LED display screen
LED is short for light emitting diode. In the PN junction of some semiconductor materials, when the injected minority carriers recombine with the majority carriers, the excess energy will be released in the form of light, thus directly converting electric energy into light energy. When reverse voltage is applied to PN junction, minority carriers are difficult to inject, so they do not emit light. This kind of diode made by injection electroluminescence principle is called light emitting diode, commonly known as led. Light-emitting diodes are diodes composed of P-type and N-type semiconductors. Near the pn junction of LED, most of the carriers in N-type materials are electrons, while most of the carriers in P-type materials are holes. When no voltage is applied to the pn junction, a certain potential barrier is formed. When a forward bias voltage is applied, under the action of an external electric field, the holes in the P region and the electrons in the N region will diffuse with each other, forming minority carrier injection, thus generating recombination of conduction band electrons and valence band holes near the p-n junction, and at the same time releasing the corresponding energy hν(h is Planck constant and ν is photon frequency) and emitting light. This energy is equivalent to the band gap energy Eg(Ev) of semiconductor materials, and its relationship with emission wavelength λ(nm) is λ= 1239. 6PEg。
LED display screen is a display screen that displays information such as words, graphics, images, animations, quotes, videos and video signals by controlling the display mode of semiconductor light-emitting diodes.
LED display screen is divided into graphic display screen and video display screen, both of which are composed of LED matrix blocks. The graphic display screen can display Chinese characters, English texts and graphics synchronously with the computer; The video display screen is controlled by a microcomputer and has pictures, words and images. It plays all kinds of information in a real-time, synchronous and clear way, and can also display two-dimensional and three-dimensional animations, videos, televisions, VCD programs and live scenes. LED display screen has bright colors, strong stereoscopic impression, static as oil painting and moving like a movie, and is widely used in public places such as stations, docks, airports, shopping malls, hospitals, hotels, banks, securities markets, construction markets, auction houses and industrial enterprise management.
Its advantages are high brightness, low working voltage, low power consumption, miniaturization, easy matching with integrated circuits, simple driving, long service life, impact resistance and stable performance.
Brief introduction of 1.2 MCS-5 1 series single chip microcomputer
1.2.1MCS-51series single chip microcomputer and its characteristics.
① High reliability:
Because the chip is designed according to the requirements of industrial measurement and control environment, its anti-interference ability is stronger than that of PC. System software (such as program instructions, constants, tables) is solidified in ROM, which is not easy to be destroyed by viruses. Multiple signal channels are integrated on one chip, and the system runs stably and reliably.
② Easy to expand:
There are components necessary for the normal operation of the computer inside the chip, and there are many pins (bus, parallel and serial input/output) outside the chip for expansion, so it is easy to form a computer application system of a certain scale.
③ Powerful control function:
There are abundant control instructions, such as conditional branch instructions, I/O port logic operation instructions and bit processing instructions.
④ strong practicability:
Small size, low power consumption, low price and easy production.
1.2.2 Brief Introduction to the Development History of Single Chip Microcomputer
① The 1 class represented by MCS-48 series (197 1 year-1978) is called a 4-bit microcontroller. On-chip: CPU has 4 or 8 bits; ROM has 1KB or 2KB；; RAM has 64B or128b; ; Only parallel interface, no serial interface; Only 1 8-bit timer; There are only two interrupt sources. Off-chip: the addressing range is only 4 KB; There are 40 chip pins.
② The second stage (1978- 1983), represented by MCS-5 1 series, is called 8-bit single chip microcomputer. On-chip: CPU has 8 bits; ROM has 4KB or 8KB；; RAM has 128B or 256B；; With serial/parallel interface; There are 2 or 3 timers with 16 bits; There are five to seven interrupt sources. Off-chip: the addressing range is 64KB；; There are 40 chip pins.
③ The third stage (after 1983), represented by MCS-96 series, is called 16-bit single chip microcomputer. On-chip: CPU has 16 bits; ROM has 8KB；; RAM has 232B；; With serial/parallel interface; There are four timers with 16 bits; There are 8 interrupt sources; D/A and A/D conversion circuits are added. Off-chip: the addressing range is 64KB；; There are 48 or 68 chip pins.
The above MCS-5 1 series have been widely used in China because of their excellent cost performance.
3. Functional requirements
A dot matrix LED graphic display screen of 16x 16 is designed for indoor use. It is required that the LED display screen has uniform and sufficient brightness under visual inspection, and can display graphics and characters, and the displayed graphics and characters should be stable, clear and without crosstalk. Graphic or text display has static, move-in and move-out display modes.
4. Scheme realization
Theoretically, we can obtain the desired display results by controlling the LED devices corresponding to the positions of the points that make up these figures or characters, regardless of whether the figures or characters are displayed. This method of controlling lighting on and off at the same time is called static driving display mode. There are 256 LEDs in 16x 16. Obviously, there are not so many ports in the single chip microcomputer. If I use latches to expand ports, the lattice of 16x 16 needs 256/8=32 latches. This number is huge, because we are only a lattice of 16x 16, and the display screen in practical application is often much larger, so the cost spent on latches will be a huge number. Therefore, in practical application, almost all display screens do not adopt this design, but adopt another display mode, called dynamic scanning.
Simply speaking, the meaning of dynamic scanning is to light up one row in turn, so that the scanning driving circuit can realize multiple rows (such as 16 rows) and one driver in the same column. Specifically, for the lattice of 16x 16, all the positive electrodes of the LEDs in the same row 1 are connected together, and all the negative electrodes of the LEDs in the same row 1 are connected together (positive electrode connection method). First, the first row of LEDs is emitted to light up the corresponding data and latch it, and then 1 is gated to execute its burning. Then send the data of the second line and latch it, then gate the second line to light up for the same time, and then close it; By analogy, after the 16 line, the 1 line lights up again, and so on. When the speed of this cycle is fast enough (more than 24 times per second), stable graphics can be seen on the display screen because of the persistence of human vision.
When scanning is used for display, there is one row driver for each row and one driver for the same column in each row. Display data are usually stored in the memory of single chip microcomputer, and are arranged in sequence in the form of 8 bits 1 byte. When displaying, the data of each column in a row should be transmitted to the corresponding column driver, which has a problem of displaying data transmission. Data transmission from the control circuit to the column driver can be in parallel or serial mode. Obviously, when the parallel mode is adopted, the number of lines from the control circuit to the column driver is large, and the corresponding amount of hardware is also large. When the number of columns is large, parallel transmission scheme is not ideal.
Using serial transmission mode, the control circuit can transmit the column data bit by bit to the column driver with only one signal line, which is undoubtedly very economical in hardware. However, the serial transmission process is long, and the data is output to the column driver one by one in sequence. Only when all the columns of a row are transferred in place can the columns of that row be displayed in parallel. In this way, the display process of a line can be divided into two parts: column data preparation (transmission) and column data display. For serial transmission mode, the preparation time of column data may be quite long, and too little time is left for row display when the row scanning period is determined, which affects the brightness of LED.
In order to solve the time contradiction between column data preparation and column data display in serial transmission, overlapping processing method can be adopted. That is, while displaying each column of data in the memory bank, the next column of data is transmitted. In order to achieve the purpose of overlapping processing, the display of column data needs to have storage function. Through the above analysis, we can get the functions that the column driving circuit should have. For column data preparation, serial-parallel shift function should be realized; For the display of column data, it should have the function of parallel latch. In this way, when the preparation data of the bank is typed into the parallel latch for display, the serial-parallel shift register can prepare the column data of the next row without affecting the display of the bank. Figure 1 is the structural block diagram of the display circuit.
Figure 1, circuit diagram of display screen
4. 1 system hardware circuit design
The hardware circuit can be roughly divided into three parts: single chip microcomputer system and peripheral circuits, column driving circuits and row driving circuits.
4. 1. 1 single chip microcomputer system and peripheral circuits
Single-chip microcomputer adopts MSC-5 1 or its compatible series chips, and adopts crystal oscillator with 24MHZ or higher frequency to obtain higher refresh frequency and more stable periodic display. The serial port of single chip microcomputer is connected with the column driver to display data. The lower 4 bits of P 1 port are connected with the row driver to send out the row selection signal; Ports P 1.5 ~ P 1.7 are used to send control signals. The P0 port and P2 port are empty, and the ROM and RAM of the system can be expanded if necessary. The hardware schematic diagram of 16x 16 dot matrix display screen is shown in Figure 2 (Appendix A).
4. 1.2 column driving circuit
The column driving circuit consists of an integrated circuit 74HC595. It has the structure of 8-bit serial input parallel output shift register and 8-bit output latch, and the control of shift register and output latch is independent, which can display the column data of the current row and transmit the column data of the next row at the same time, not only achieving the purpose of overlapping processing.
The external shape and internal structure of 74HC595 are shown in Figure 3. Its input has eight serial shift registers, and the output of each shift register is connected to an output latch. Pin SI is the input of serial data. Pin SCK is a shift clock pulse of the shift register, which shifts at its rising edge and drives the next data of SI to the lowest bit.
The shift signal of each bit appears at the output of each shift register, that is, at the input of the output latch. RCK is the input signal of the output latch, and its rising edge inputs the output of the shift register to the output latch. The G-pin is the opening signal of the output tri-state gate, and the output of the latch is only opened at low level, otherwise it is configured at high level. The SCLR signal is the clear input of the shift register. When it is low, the output of the shift register is all zero. Because the SCK and RCK signals are independent of each other, the input serial shift and output latch will not interfere with each other. The output terminal of the chip is QA ~ QH, and the highest bit QH can be used as the cascade output of multiple pieces of 74HC595. However, since QH is controlled by the input of the output latch, QH is also extracted from the front end of the output latch as a cascaded output completely synchronized with the shift register.
QB 1 16
QC 2 15 QA
QD 3 14 SI
Qe413g
QF 5 12 RCK
QG 6 1 1 SCK
QH 7 10 SCLR
GND 8 9 QH
Figure 3. Shapes and pins of 74HC595
4. 1.3 line driver
The low-order 4-bit line number output from the P 1 port of the single chip microcomputer is decoded by the 4/ 16 line decoder 74LS 154 to generate the 16 line strobe signal, and then the corresponding line is driven by the driver. A row line needs to drive 16 columns of LEDs for display. According to the 20MA current of each LED device, when 16 LEDs emit light at the same time, 320MA current is needed, and the gating transistor 8550 can meet the requirements as a driving tube.
4.2. System Programming
The main function of the display screen software is to provide display data to the screen body and generate various control signals, so that the screen can be displayed according to the design requirements. According to the principle of software layered design, the software system of display screen can be divided into two layers; The first layer is the bottom display driver, and the second layer is the upper system application. The display driver is responsible for sending display data to the screen body, generating line scanning signals and other control signals, and cooperating with the LED display screen to complete the scanning and display work. The display driver is realized by timer interrupt program. The system application program completes the system environment setting (initialization), display effect processing and other work, which is realized by the main program.
Considering that it is beneficial to realize more complex algorithms (display effect processing) and the structure of the program, the display screen program is suitable to be written in C language.
4.2. 1 display driver
After the display driver is interrupted, it is necessary to re-assign the initial value to the timer T0 to ensure the stability of the refresh rate of the display screen. The formula for calculating the refresh rate (frame rate) of116 scanning display screen is as follows:
Brush frequency (frame rate) =116× t0 overflow rate
= 1/ 16×f/ 12(65536-t)
Where the frequency of the f-bit crystal oscillator, t is the initial value of the timer T0 (working in 16-bit timer mode).
Then the display driver queries the currently lit line number, reads the display data of the next line from the display buffer, and sends it to the shift register through the serial port. In order to eliminate the tailing phenomenon when switching lines to display data, the driver should first close the display screen, that is, blank it, wait for the display data to be typed into the output latch and latched, then output a new line number and reopen the display. Fig. 4 is a flowchart of a display driver (display screen scanning function).
Figure 4 shows the driver flow chart.
4.2.2 System main program
The system software designed in this paper can make the brightness of LED display screen uniform and sufficient under visual inspection, and can display graphics and characters, which should be stable, clear and without crosstalk. Graphic or text display has static, move-in and move-out display modes.
After the main program of the system is started, the system environment is initialized, including setting serial port, timer, interrupt and port. Then display the graphics with the effect of "rolling out" and stay for about 3 s; Then scroll up to display five Chinese characters and a graphic of "I love single chip microcomputer", and then hide the graphic with the effect of "rolling in". Because the single chip microcomputer has no stop instruction,
Therefore, the system program can be set to continuously and cyclically perform the above display effect.
The unit display screen can receive data information and command information transmitted from the controller (main control circuit board) or the upper display unit module, and can transmit these data information and command information to the lower display module unit without making any changes, so the display panel can be extended to more display units to display more display contents.
Fig. 5 is a flowchart of the main program of the system.
Fig. 5 Flow chart of main program of the system
5 Performance analysis and summary
5. Performance analysis of1
As long as the hardware quality of LED display screen is reliable and the pins are welded correctly, it can work normally without debugging. Software debugging mainly includes two parts: display refresh frequency and display effect. The refresh rate of the display screen is determined by the overflow rate of timer T0 and the crystal frequency of the single chip microcomputer. Table 5. 1 gives the frequency used in the experimental debugging and the corresponding initial value of timer T0.
Table 5. 1 shows the relationship between the flat refresh rate and the initial value of T0 (24MHz crystal oscillator).
The refresh rate is 25 50 62.5 75 85100120
T0 0xeC78 0xF63C 0xF8300xf97E0XFA420XFB65438+E0XFBee Initial Value
Theoretically, when the refresh rate is higher than 24Hz, a stable and continuous display can be seen. The higher the refresh rate, the more stable the display is, and the higher the refresh rate, the more CPU time the display driver takes up. Experiments show that under the visual condition, the picture with refresh frequency below 40Hz looks more flickering, while the picture with refresh frequency above 50Hz is almost imperceptible. When the refresh frequency is above 85Hz, there is no obvious improvement by adding picture flicker.
The contents and methods of the display effect handler are very extensive, so we will not discuss its debugging process in detail here. Readers can analyze it by themselves according to the source program.
The 16x 16 dot matrix LED graphic display screen designed in this scheme is simple in circuit, low in cost and easy to expand into a larger display screen. The brightness of the display screen is even and sufficient; The displayed graphics or characters are stable, clear and free from crosstalk; Graphics or characters can be displayed in various display modes, such as static, moving in and moving out.
5.2 Summary
An indoor dot matrix LED graphic display screen of 16x 16 designed in this paper can display graphics and characters with uniform brightness under visual conditions, and the displayed graphics and characters should be stable, clear and crosstalk-free. Graphic or text display has static, move-in and move-out display modes. The system has the characteristics of less hardware, simple structure, easy implementation, stable and reliable performance and low cost.
Summarizing the research work of this paper, I have mainly done the following outstanding work:
1. By consulting a large number of relevant materials, we have learned in detail the luminous principle of LED and the principle of LED display screen, understood the current situation of LED, and clearly understood how LED display screen compares with other display screens.
Advantages, clear research objectives.
Secondly, the LED display screen designed in this paper can achieve uniform and sufficient brightness of the LED display screen under the condition of visual inspection, and can display graphics and characters, and the displayed graphics and characters should be stable, clear and crosstalk-free. Graphic or text display has static, move-in and move-out display modes.
Thirdly, the paper gives the specific hardware design scheme, hardware structure circuit diagram, software flow chart and specific assembly language program design and debugging.
Fourthly, I learned the basic use of Protel 99se in the process of graduation design, and felt that Protel 99se was a very useful course for students majoring in automation.
Fifth, through this graduation project, I reviewed and further studied MCS-51; Mastered the use of WORD software.
Sixth, there are defects: the problem of anti-interference is not considered.
Express gratitude/gratitude
This paper was completed under the careful guidance of Mr. Jin Ming. Every step of the work, from project establishment and topic selection to project development and research, and then to the writing and finalization of this paper, has been devoted to Mr. Huang's hard work and sweat, and at the same time, he has been helped by his classmates and provided a lot of information. Here, I would like to express my heartfelt thanks to the teachers and classmates for their help.
refer to
[1] He Limin. Application system design and interface technology of MCS-5 1 series single chip microcomputer. Beihang press, 1990.
[2] Ren Tao et al. A Concise Handbook of Flash Data and Its Application. Electronic Industry Press, 1997.
[3] He Limin. Selected applications of single chip microcomputer. Beijing University of Aeronautics and Astronautics Press, 2000
[4] Zhang et al. MCS-5 1 Application Design of Single Chip Microcomputer. Harbin Industrial Electronics Press, 1996
[5] Wu Kuanming. Practical handbook of peripheral equipment of single chip microcomputer. Beihang Press, 1998.
[6] Zhang Kai. LED introduction complete manual. Beijing University of Aeronautics and Astronautics Press, 2000.
[7] Zhang Youde et al. Application and Experiment of Single Chip Microcomputer Principle, Fudan University Press, 1996.
Appendix A Hardware Schematic Diagram of Dot Matrix LED Graphic Display 16x 16
Appendix b list of main assemblers
The following is the source program of 16x 16 dot matrix LED electronic graphic display screen, which is written in assembly language (or C language), and the C program has been debugged in KeiluVision2 V2.30 environment.
The following is a character display control program written in assembly language:
; ***************************************
; * *
; * Single 16x 16 dot matrix electronic screen character display *
; * ATA89C52 12MHz crystal oscillator *
; * LRM *
; ***************************************
; Look-up table method is used to display characters, which does not occupy memory, and the characters use 16x 16 * * positive LED lattice.
; Effect: Scroll up to display 5 words, and then repeat the cycle.
; R 1: lookup table offset register, b: lookup header address, R2: scan address (from 00 to 0fh).
; R3: Control the moving speed when scrolling, and the time of static display can be controlled by single-character display.
; *************;
; Interrupt entry procedure;
; *************;
ORG 0000H
LJMP start
ORG 0003H
Retty
ORG 000BH
LJMP INTTO
ORG 00 13H
Erti
ORG 00 1BH
Erti
ORG 0023H
Retty
ORG 002BH
Retty
; ***********;
; Initialization program;
; ***********;
; ***********;
; Main program;
; ***********;
Starting: MOV 20H, # 00H clears the mark, 00H is the start scanning mark of line 16, and 0 1 is the 1 frame.
; Scan end flag
MOV A, # 0FFH port initialization
MOV P 1，A
MOV P 1，A
MOV·P3
MOV P0，A
CLR p 1.6； Serial register input/output control bit
MOV TMOD，# 0 1H； Use T0 as the 16-bit timer for line scanning.
The initial value of MOV TH0 and # 0FCH is 1 ms (12mhz).
MOV TL0，# 18H
MOV SCON, # 00H serial port 0 mode transmission display byte.
MOV IE, # 82H allows T0 interrupt and allows total interrupt.
MOV SP，#70H
Lord: LCALL DISI；; Display preparation, black screen, 1.5s
MOV DPTR, # tag
LCALL MOVDISP scrolls up to display one page (8 words).
DPH Company
LCALL MOVDISP scrolls up to display one page (8 words).
DPH Company
LACLL MOVDISP scrolls up to display one page (8 words).
AJMP manager
; ***********************;
; Multi-word scrolling display program;
; ***********************;
; Eight words at a time, the DPTR value is defined at the entrance.
MOVDISP: MOV B, # 00H Move the display screen upward, and temporarily find the workbench deviation value (starting from 00).
Dislocation: MOV R3, # 07H moving speed
Dismov: MOV R2, 00h；; Starting from line 0
MOV R 1，B
SETB TR0； Open scanning (one frame at a time)
Witmov: JBC 0 1H, desmov1; Mark 1 to complete a frame scan (1 frame 16ms, each line 1ms).
AJMP Wymov
DISMOV 1: DJNZ R3, dismov1frame repeat display (control moving speed)
INC B； Displays the next line of the word (2 bytes per line)
Company b
MOV A，r 1； R 1 is 0, and 8 words are displayed.
Jz moft
AJMP dislocation
mov out:RET； The movement ends first.
; ****************;
; Single character display program;
; ****************;
; Display words in a table;
; ****************;
DIS 1: MOV R3, # 5AH static display time control (16ms * # = 1.6 seconds)
DIS 1 1: MOV R2, # 00H Initial scan value of a frame (line address from 00 to 0fh)
MOV·DPTR, # TAB takes the first address of the table.
MOV R 1, # 00H lookup table offset (first word displayed)
SETB TR0； Open scanning (one frame at a time)
wait 1 1:JBC 0 1H，dis 1 1 1； For 1, one frame of scanning ends.
AJMP wait 1 1
Diss 1 1: djnzr3, diss11
Soak in water to soften
; ************;
; Scanning program;
; ************;
; 1ms is refreshed once, and 1 is displayed on each line.
INTT0: press ACC.
MOV TH0, # 0FCH 1 millisecond initial value overload
MOV TL0，# 18H
JBC 00H, GOEND, the scanning mark of line 16 is 1, and it is over.
INC r 1； Take the byte offset to the right of the line.
MOV A，R 1
MOVC A，@ A+DPTR； table look-at
MOV· Spoff; Serial port 0 mode transmission
Wait: JBC, go; Wait for the transmission to complete.
AJMP WAIT 1
GO:DEC r 1； Take the byte offset to the left of the line.
MOV A，R 1
MOVC A，@A+DPTR
MOV· Spoff
WAIT 1: JBC T 1，GO 1
AJMP WAIT 1
go 1:SETB p 1.7； Close the display and prepare to refresh.
Data stability of NOP serial port register
SETB p 1.6； A rising edge is generated, and line data is input to the output terminal.
Nototherwiseprovided(for) unless otherwise specified.
Nototherwiseprovided(for) unless otherwise specified.
CLR p 1.6； Restore to a low level
MOV A，R2； Modify the display line address
ORL A, # 0F0H Modify the display line address
MOV·R2； Modify the display line address
MOV A，p 1； Modify the display line address
ORL A, # 0FH Modify the display line address.
ANL A，R2； Modify the display line address
MOV P 1，A； Modification completed
CLR p 1.7； Line display
R2 company; Next line scan address value
INC R 1
INC r 1； Next line data address
R2 MOV
ANL A，#0FH
JNZ GO2
SETB 00H； R2 is 0 1H, and now the last line is scanned and marked.
GO2: Pop up ACC
Retty
GOEND:CLR TR0； After scanning a frame, turn off scanning.
SETB 0 1H； After scanning a frame, set the end flag.
Popular ACC
RETI； give up
; ***************;
; Scan text list;
; ***************;
TAB:DB 0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，00FFH，0FFH，0 ffh； blank screen
decibel
0F9H，0BFH，0C7H，0AFH，0F7H，0B7H，0F7H，0B7H，0F7H，0BFH，000H，00 1H，0F7H，0BFH，0F7H，0B7H； I
decibel
0F 1H，0D7H，0C7H，0CFH，037H，0DFH，0F7H，0AFH，0F6H，06DH，0F7H，0F5H，0D7H，0F9H，0EFH，0FDH
decibel
0fh, 007H, 0C0H, 06FH, 0EDH, 0EFH, 0F6H, 0DFH, 0C0H, 00 1H, 0DDH, 0fh, 0C0H, 003H love.
decibel
0FBH，0FFH，0F8H，00FH，0F3H，0DFH，0F4H，0BFH，0EFH，03FH，09CH，0CFH，073H，0F 1H，0CFH，0 fbh；
decibel
0F7H，0DFH，0F9H，0CFH，0FBH，0BFH，0C0H，007H，0DEH，0F7H，0C0H，007H，0DEH，0F7H，0DEH，0 DEH，0F7H； single
decibel
0C0H，007H，0DEH，0F7H，0FEH，0FFH，000H，00 1H，0FEH，0FFH，0FEH，0FFH，0FEH，0FFH，0FFH，0FEH，0 ffh
decibel
0FFH，0BFH，0EFH，0BFH，0EFH，0BFH，0EFH，0BBH，0E0H，00 1H，0EFH，0FFH，0EFH，0FFH，0FFH，0EFH，0 efh，0 efh，0 ffh，0 ffh； piece
decibel
0E0H，00FH，0EFH，0EFH，0EFH，0EFH，0EFH，0EFH，0EFH，0EFH，0BFH，0EFH，07FH，0FFH
decibel
0EFH，0FFH，0EFH，007H，0EFH，077H，00 1H，077H，0EFH，077H，0EFH，077H，0C7H，077H，0CBH，077h； machine
decibel
0ABH，077H，0AFH，077H，06EH，0F7H，0EEH，0F5H，0EDH，0F5H，0EDH，0F5H，0EBH，0F9H，0EFH，0FFH
decibel
0FH, 0FH, 0FH, 0FH, 0FH, 0FH, 0FH, 0FH, 0FH, 0FH, 0FH, 0FH, 0FH, 0FH, 0FH, 0FH, 0FFH, black screen.
decibel
0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0FFH，0 ffh，
end