Complete System Level Block Diagram

 

Written by:

Jamie Buckmann and Christopher Stedman

 

Advised by:

Mr. Steven Gutschlag 

 

A system level block diagram for the project entitled “Microcontroller Driven Electroluminescent Display” is shown in Figure 1.  The inputs from the formula car and the user are sent to the microcontroller.  The microcontroller processes the inputs and makes any updates to the electroluminescent display indirectly through the LCD controller.    The following sections identify the subsystems shown in Figure 1 as well as their functions.

 

 

Figure 1: System Level Block Diagram

 

AMD’s 80C31 Microcontroller (Block 1)

The 80C31 microcontroller is responsible for deciphering the input signals and updating the LCD Controller accordingly.  The microcontroller block includes program memory and data memory.  They are interfaced trough the multiplexed data bus with the help of a 74ALS573 latch.  The microcontroller can receive and send signals over both digital pins and the address/data bus.

Figure 2: AMD’s 80C31 Microcontroller Subsystem Block Diagram (Block 1)

 

Microcontroller Inputs

Function

Ignition Signal

The frequency of the ignition signal will be used to determine the rotations per minute (RPM) of the engine.

Front Tire Sensor

The rotational speed of the front tire will be calculated to find the ground speed of the vehicle.  This will also be used in conjunction with the ignition signal to find the current gear.

Digital Inputs from Engine Control Unit

Digital input from the engine control unit.  It signals low oil pressure.

Analog Inputs

The microcontroller receives up to eight analog inputs from the ADC0808.  The ADC0808 is interfaced to the address/ data bus.  Individual inputs will be explained in ADC0808 block.

Keypad Press

The keypad encoder can interpret up to 20 keys.  It is interfaced to the address/data bus.  When a key is pressed, it places the binary coded key value on the data bus for the microcontroller to read.

Table 1: Microcontroller Inputs

 

Microcontroller Output

Function

Digital Outputs

Port 1&3

All digital outputs on port 1 and port 3 will be used for many miscellaneous tasks handled by the microprocessor.

Output to LCD Controller

The microcontroller communicates to the LCD controller over the address/data bus.  It specifies what pixels need to be on, and the LCD controller takes care of the communication to the display.

Table 2: Microcontroller Outputs

LCD Controller (Block 3)

The LCD Controller subsystem (Figure 3) interfaces microcontroller to the display.  It has the capabilities of displaying layered text and graphics, scrolling the display in any direction, and partitioning the screen into multiple screens.  It is responsible for continually updating the electroluminescent display and storing the current display in external memory

 

 

 

Figure 3: LCD Controller Subsystem Block Diagram (Block 3)

 

Microcontroller Inputs to LCD Controller

Function

A0

Selects the data type to be displayed.

CS’

Activates the LCD controller when the microcontroller is accessing external memory that is associated with the LCD controller.  The logic decoding hardware handles the memory mapping.

AD[0:7]

The data bus is used to transfer bi-directional data between the microcontroller and the LCD controller

RD’

Control signal used during read cycles.

WR’

Control signal used during write cycles.

RES’

Reset signal to initialize LCD controller.

Table 3: Microcontroller Inputs to LCD Controller

 

External RAM Interface

Function

VA0 – VA14

Determines which memory address of the external RAM is specified.

VD0 – VD7

Reads or writes to the specified address.

VR/W’

VRAM R/W Signal

VCE’

Memory Control Signal

Table 4: Controller Outputs to External RAM Interface

 

Electroluminescent Display Interface

Function

XD0 – XD3

X-Driver Data: Data signals to the Electroluminescent Display

XECL

X-driver enable chain clock

XSCL

Data shift clock to update data at determined time intervals.

LP

Latch pulse so screen is not read while being written to.

WF

Frame signal.

YDIS

This signal turns off the display if the screen is blanked.

YD

Scan start pulse.

YSCL

Y-driver shift clock

Table 5: Controller Outputs to Electroluminescent Display Interface

 

Decoding Logic Subsystems (Block 2)

The decoding logic is required to organize all devices using the address/data bus in memory space.  The decoding logic subsystem block diagram can be seen in figure 4.  Specific memory location are assigned for the LCD controller, A/D write, A/D read, and keypad encoder in the microcontroller’s memory map (figure 5)  It is also responsible for creating a 500 kHz square wave for the A/D conversion.  All output signals are explained with their respective devices.

 

 

Figure 4: Decoding Logic Subsystem Block Diagram (Block 2)

 

Figure 5:Memory map partitions created by decoding logic (Block 2)

 
Electroluminescent Display Subsystem (Block 4)

This subsystem displays data and graphics based on information received from the LCD Controller.  The only output is what is displayed on the screen.  The signal labeled YDIS, from Table 5, is used to turn off the electroluminescent display when the screen is blank.  The voltage regulator maintains a constant voltage for the display and is easily controlled by the YDIS signal.  All other inputs and their functions are listed in Table 5.  Figure 6 shows the block diagram for this subsystem.

 

Figure 6: Electroluminescent Display Subsystem Block Diagram

 


Static RAM Subsystem (Block 5)

The external RAM is used to store text, character codes, and bit-mapped graphics data for the LCD Controller.  The LCD Controller determines the address of the desired information and then reads the data.  All of the inputs and outputs are described in Table 4, as well as a block diagram in Figure 7.

 

 Figure 7: Static RAM Subsystem Block Diagram (32,768-word x 8-bit)

 

A/D and Signal Conditioning Subsystems (Block 6 & Block 8)

The A/D’s communication with the microcontroller is broken into two processes.  To start the conversion data is written to the memory address that correlates to the A/D and correct analog signal.  The signal number is chosen by A10 through A8 as seen in Figure 8.  Once the conversion is completed the A/D generates an interrupt with the EOC signal.  The microprocessor responds by reading from the memory location associated with the A/D.  The data received from the A/D ranges from 00h = 0V to FFh = 5V.  All signal conditioning will be done off of the board to add flexibility in choosing analog inputs.    

 

Figure 8: Multiplexed Input Analog to Digital Subsystem Block Diagram (Block 6) and

Signal Conditioning Subsystem Diagram (Block 8)

 

Inputs

Function

ALE & START

Signal initiates A/D conversion.

OE

Signal to put converted data on the data bus.

CLOCK

500 MHz clock signal.

A8-A10

Analog signal select lines.

Analog Inputs

IN0 - O2 sensor signal

IN1 – Temperature thermocouple signal

Table 6: Inputs to A/D converter

 

Outputs

Function

AD[0:7]

Outputs digital value of analog signal to data bus.

EOC

End of calculations signal.  Causes interrupt to handle reading the data bus.

Table 7: Outputs to A/D converter

 Keypad Encoder Subsystems (Block 7)
       
When a key is pressed the encoder uses the row and column inputs to decipher what key was pressed.  The encoder then enables the DAV signal, which generates an interrupt signal on the microcontroller.  The microcontroller responds by reading from the memory location associated with the keypad encoder.  The binary key value is placed on AD[0:4] for the microprocessor to read.

 

 

Figure 9: Keypad Encoder Subsystem Block Diagram (Block 7)

 

Inputs

Function

OE’

Signal to enable key value on the data bus.

ROW

Signal to tell encoder what row was pressed.

COLUMN

Signal to tell encoder what column was pressed.

OSC

Capacitor value sets polling frequency.

KBC

Capacitor value sets key debounce period.

Table 8: Inputs to keypad encoder

 

Outputs

Function

AD[0:4]

Outputs digital value of key pressed to data bus.

DAV

Data available signal.  Causes interrupt to handle reading the data bus

 Table 9:Outputs to keypad encoder