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Part: AN442
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Philips Semiconductors Microcontroller Products
Application note
(BCM) 87C751 Specification for a bus-controlled monitor
AN442
SUMMARY
BCM87C751 is a powerful, flexible and low cost Digital Controlled Monitor System, based on the 87C751 microcontroller. It employs I2C bus control with various I2C bus controlled peripherals (PCF8582EP-EEPROM and TDA8444 D/A converter). The control function is implemented via 8 6-bit DC voltage output from TDA8444. Some features of the system: · Flexible approach, especially for multisync or auto sync operation · Mode detection and frequency measurements by microprocessor · Mode switching under software control · Elimination of potentiometers · Quick factory alignment (DACs can be preset) · Automatic factory alignment possible This document describes the operation and the use of the system. it provides necessary information concerning operation, required hardware, flow charts and their effect on the performance.
The system can perform the following: Determine the mode and standard of incoming signals with the stored values in memory (e.g., multisync modes). Enter parameters of user defined modes into memory via a keyboard. Control analog parameters such as contrast and brightness via the bus from keyboard inputs. Control mode and standard parameters (such as picture geometry parameters and the free-running oscillator frequency).
· Four outputs of Horizontal PLL capacitor selection signal. This can be easily adapted for further extension.
IC DESCRIPTIONS
87C751 A derivative of the 8051 family of microcontrollers, the 87C751 has an 8-bit CPU, 2k bytes EPROM, 64 bytes RAM, 19 I/O lines, a bi-directional inter-integrated circuit (I2C) serial bus interface, and an on-chip oscillator. PCF8581/2 A 1k- or 2k-bit, 5V electrically erasable programmable read only memory (EEPROM) organized as 128 or 256 × 8 bits. The stored information is electrically alterable on a word-by-word basis, I2C-bus controlled. TDA8444 Comprises eight DACs, each controlled via the I2C-bus. The DACs are individually programmed using a 6-bit word to select an output from one of 64 voltage steps. the maximum output voltage of all DACs is set by the input VMAX and the resolution is approximately VMAX/64. For detailed information on these devices, please refer to their respective data sheets.
Features
· Multisync or Autosync operation FH = 31kHz95kHz FV = 50Hz114Hz · Selectable four or five function control configurations · Selectable one digit, or one and one-half digit, or null seven segment mode display. · Selectable Horizontal direct ratio or indirect ratio F to V converter DAC output configurations · Selectable ten user modes plus ten factory modes, or, one user mode plus 19 factory modes configurations · Selectable multiple up/down keys or minimum keyboard configuration · Change function without save key, all keys but the reload key have a repeat function · Both Horizontal and Vertical outputs have F-to-V converter DAC outputs
INTRODUCTION
Figure 1 shows the block diagram of a high-performance color monitor with microcontroller and several parts that communicate via the two-wire I2C-bus.
I2 C
DAC TDA8444
R.G.B.
VIDEO PREAMP. TDA4880
VIDEO OUT. STAGE
R G B
CRT
I/O H SYNC HORIZONTAL PROCESSOR TDA4810 HORIZONTAL OUT. STAGE
I2 C
DAC TDA8444 V SYNC VERTICAL DEFLECTION TDA4800 I2 C I/O I2 C
EAST WEST STAGE TDA1082
87C751 MICROCONTROLLER
EEPROM PCF8582
LED DRIVER HEF4511
Figure 1. Block Diagram of Bus Controlled Monitor System BCM 87C751
December 1991
1
Philips Semiconductors Microcontroller Products
Application note
(BCM) 87C751 Specification for a bus-controlled monitor
AN442
OPERATION INSTRUCTION Function Selection and Change
When the monitor is powered on it will automatically enter the corresponding mode depending on the input signal. Different configurations and functions can be defined by users with the use of different features. The following configuration's functions are examples for user's reference. See Figure 2 for Configurations 1 through 4. To adjust functions such as V-size, V-shift, H-center, H-shift, and PCC (Pincushion Correction Circuitry): 1. The "Function" key should be pressed until the required function LED is lit. 2. If the V-shift LED is on, the user can then adjust V-shift by pressing Up or Down key. If the Up key is pressed, the V-shift DAC output will increase one step. While the Down key is pressed, the V-shift DAC output will decrease one step. The user can repeat the Up or Down key simply by pressing it longer than 0.5 second. It will then automatically repeat approximately 2 times per second until the key is released.
Each number denotes one mode. Modes 10 through 19 are user modes, which can be defined by the user. When there is a new mode entering the monitor that does not belong to any mode stored n the EEPROM, the mode display will show "19". If the user presses the Reload key while the mode display is "19", the display will flash. When the mode display is flashing, the user can select the destination mode by pressing the Up/Down keys. The destination mode is between 10 and 19. Every press of the Up key causes the flashing display to add one, unless it already reached 19. Every press of the Down key causes the flashing display to subtract one, unless is has reached 10. When the user lets the destination mode flash on the display, the user can press the Reload key to store the new mode to destination mode. When the mode display stops flashing, the new mode is stored. The newly stored destination mode is permanent, unless the user repeats the entire procedure. To change an old user mode, already stored in EEPROM, to a different user mode, press the Reload key for longer than 8 seconds while the monitor is working in the old mode. The mode display will flash the old mode, then the user can use the Up/Down key to select the new mode. Press the Reload key again to copy the old to new destination user
mode. If the user forgets to press the Reload key again, the flashing of the mode display will last for 2 minutes, then the program will cancel the copy old mode to new user mode command. During the flash period, the program still monitors the Horizontal and Vertical sync signal to adapt the DAC to the proper mode. For example, while the user tries to copy new mode 13 to mode 15, and the mode display 13 (15) is flashing, if the PC sends out a signal for mode 3, the program will change the DAC output to adjust the monitor to work in mode 3, but the mode display is still flashing on user mode 13 (15) and the store procedure is still going on until the user presses the Reload key again, or terminates the copy procedure after the 2 minutes time out. The mode display then shows 3. NOTE: Upon request, we can also program in advance those 10 user-defined modes that can still be changed by the user if necessary for further extension. For Configuration 5 to Configuration 8, see Figure 3. To adjust functions, the user can simply press the corresponding push button. The upper push button will increase the DAC output. The lower push button will decrease the DAC output. (A total of 64 steps can be programmed in advance.)
Mode Selection and Change
(See Figure 4) In Figures 3 and 4. the mode number is displayed on the two seven-segment LEDs.
CONFIGURATION 1 FUNCTION UP DOWN RELOAD 1. 2. 3. 4. ( FUNCTION ) 5.
CONFIGURATION 2 FUNCTION UP DOWN RELOAD 1. 2. 3. 4. ( FUNCTION ) 5.
CONFIGURATION 3 FUNCTION UP DOWN RELOAD 1. 2. 3. 4. ( FUNCTION )
CONFIGURATION 4 FUNCTION UP DOWN RELOAD 1. 2. 3. 4. ( FUNCTION )
Figure 2. Control Panel
December 1991
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Philips Semiconductors Microcontroller Products
Application note
(BCM) 87C751 Specification for a bus-controlled monitor
AN442
CONFIGURATION 5 RELOAD
H-WIDTH
H-CENTER
V-SIZE
V-SHIFT
CONFIGURATION 6 RELOAD
H-WIDTH
H-CENTER
V-SIZE
V-SHIFT
CONFIGURATION 7 RELOAD
H-WIDTH
H-CENTER
V-SIZE
V-SHIFT
PIN
CONFIGURATION 8 RELOAD
H-WIDTH
H-CENTER
V-SIZE
V-SHIFT
PIN
Figure 3. Control Panel
MODE 0 1 2 3 4 5 6 7 8 9 10 · 18 19
NAME VGA-1 VGA-2 VGA-3 8514A SVGA-1 UVGA-1 VESA V64-1 SVGA-2 V78 USER DEFINE · · ·
H.F. 31k 31k 31k 35k 35k 48k 56k 64k 37k 78k · · · ·
V.F. 70 70 60 87 56 60 70 60 60 60 · · · ·
H.P. + + + + + + + · · · ·
V.P. + + + + + + + · · · ·
Figure 4. Mode Selection
December 1991
3
Philips Semiconductors Microcontroller Products
Application note
(BCM) 87C751 Specification for a bus-controlled monitor
AN442
SOFTWARE FLOW CHART DESCRIPTION
(See Figures 5 through 7) When power is on, software initializes the hardware first. The microcontroller waits 100µs for the settlement of the hardware, then initializes itself by specifying stack, setting timer, clearing RAM, arranging interrupt, . . . , etc.
START
CONFIGURATION
EEPROM BLANK N
Y
PROGRAM EEPROM
RELOAD PREVIOUS MODE DATA
FUNCTION SELECTION N0 KEY PRESSED
KEY PRESSED
A
0.5 SECOND TIME OUT
MODE DETECTION C
B
DISPLAY FUNCTION & MODE
Figure 5. Main Flow Chart
December 1991
4
Philips Semiconductors Microcontroller Products
Application note
(BCM) 87C751 Specification for a bus-controlled monitor
AN442
A
FUNCTION KEY N
Y
N
RELOAD KEY Y
UP/DOWN KEY PROCESS
LAST USER MODE Y
N
Y
FLASH FLAG SET N
FIRST PRESS N
Y
CHANGE FLASH MODE
EEPROM FUNCTION DATA ± 1
CLEAR FLASH FLAG
SET FLASH FLAG
PUT ROM DATA TO EEPROM
FUNCTION +1
OUTPUT TO DAC
GET LAST MODE DATA
OUTPUT TO DAC
OUTPUT TO FLASH MODE
C
Figure 6. Function Selection Flow Chart
December 1991
5
Others parts begin by an
AN-1 AN-2 AN-3 AN-4 AN-5 AN-6 AN-7 AN-8
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