9. TkGate Library Components

The TkGate distribution includes four libraries that can be loaded through the library manager. Components from these libraries can be used to add additional functionality to your designs. To use one of the libraries, open the library manager with the toolbar button and select the library you wish to load. You can then locate the module you wish to use in the module hierarchy and drag it onto the main window canvas to create an instance of it. The libraries that are available with TkGate are described in the following sections.

(Click to Enlarge)

Figure 9.2: TTY Device Window

Figure 9.1:
TTY Device

To use the TTY device, open the library manager with the toolbar button and load the "tty" library. You can then locate the module in the module list or module hierarchy and drag it onto the main window canvas to create an instance of it. Figure 9.1 shows the external view of the TTY instance which is defined with a symbolic module interface.

When a design containing the TTY device is simulated, it will open a window such as the one shown in Figure 9.2 (after the design has been running for a while). The text shown in this window was transmitted from the "Menagerie CPU" example. Keys pressed while the window has focus will be transmitted back to the controlling design.

Figure 9.3:
Transmit Character

Figure 9.4:
Receive Character

  initial
    begin
      # 10000 ;
      $tkg$send("main.memory.tty0.FORCE","Hello World");
  end

Figure 9.5: Drink Machine Device


(Click to Enlarge)

Figure 9.6: Drink Machine GUI

To use the drink machine device, open the library manager with the toolbar button and load the "coke" library. You can then locate the cokemachine module in the module hierarchy and drag it onto the main window canvas to create an instance of it. Figure 9.5 shows the external view of the cokemachine instance.

The virtual drink vending window that appears when you start the simulation is shown in Figure 9.6. It is comprised of an external view (left side) and an internal view (right side). The external view includes buttons that can be pressed to make a drink selection, a coin slot, and a bill reader.

The following interactions can be made through the drink machine GUI:

• Coins are inserted by dragging them from the user's stock of cash in the upper left corner to the coin slot.
• Bills are inserted by dragging them from the user's stock of cash in the upper left corner to the bill reader.
• Fake bills can be dragged to the bill reader to test if the control logic detects and rejects them correctly.
• Drink selections are made by pressing the drink buttons on the external view.
• Pressing the coin return lever should cause inserted coins to be returned.
• Purchased drinks appear in the margin along the bottom.

The internal view shows the columns of drinks that are available in the machine, the status of the bill scanner, the coins that have been inserted (but not used for a purchase), the coins that have been committed to a purchase, and coins that are available to make change.

The input signals on the drink machine and their function are as follows:

Signal	Description
DISP	Dispense - Each of the six bits dispenses a drink from one of the six columns. Drinks are dispensed on the rising edge of the signal. Only one bit should be asserted at a time, and only after ensuring the the DISPACK (Dispense Acknowledge) signal is low. The asserted bit should remain high until the DISPACK signal goes high.
ELIGHT	Empty Light - Each bit corresponds to the empty light on each of the six buttons. If a bit is asserted, then the corresponding empty light will be illuminated.
CHGQ CHGD CHGN	Dispense Change - Drop a quarter (CHGQ), dime (CHGD) or nickel (CHGN) from the "Change" bin. Only one of these signals (or the CHGCOM or RETINS signals) may be asserted at a time. Change is dropped on the rising edge of the signal. The signal should not be raised unless the CHGACK (Change Acknowledge) signals is low. The Dispense Change signal should be held high until the CHGACK signal goes high.
NOCHG	No Change - If asserted, illuminates the "No Change" light on the vending machine to indicate that change can not be made.
BILLIN	Bill In - Drives the bill motor to feed the inserted bill into the bill tester. Bills in the bill tester will be dropped into the "Collected" bin. The motor is activated on a positive edge of this signal. This signal should not be raised unless the BILLACK (Bill Acknowledge) signal is low. The Bill In signal should be held high until the BILLACK signal goes high.
BILLLT	Bill Light - This signal illuminates the light on the bill reader.
BILLOUT	Bill Out - Drives the bill motor to feed out the bill currently in the bill tester. The motor is activated on a positive edge of this signal. This signal should not be raised unless the BILLACK (Bill Acknowledge) signal is low. The Bill Out signal should be held high until the BILLACK signal goes high.
CHGCOM	Change Commit - This signal commits any change in the "Inserted" area to the "Collected" area. Change is committed on the rising edge of this signal. The signal should not be raised unless the CHGACK (Change Acknowledge) signals is low. The Dispense Change signal should be held high until the CHGACK signal goes high.
RETINS	Coin Return - This signal returns any change in the "Inserted" area back to the user. Change is returned on the rising edge of this signal. The signal should not be raised unless the CHGACK (Change Acknowledge) signals is low. The Dispense Change signal should be held high until the CHGACK signal goes high.
INSACK	Insert Acknowledge - This signal should be raised after seeing a positive edge on the INSQ, INSD or INSN signals indicating that a coin was inserted.
COST	Drink Cost - This signal drives the drink cost displayed on the external view of the vending machine. It should be the cost in nickels.
RESET	Reset - Resets the drink machine. This is an active low signal. It should be driven low to reset the machine, then kept high while using the device.

The output signals on the drink machine and their function are as follows:

Signal	Description
PRESS	Button Pressed - Each bit is for one of the six buttons on the drink machine and is asserted while the corresponding button is pressed.
EMPTY	Empty Sensor - Each bit corresponds to one of the drink columns and is asserted when the sensor indicates that there are no more drinks in a column.
INSQ INSD INSN	Coin Inserted - These signals indicate that a quarter (INSQ), dime (INSD) or nickel (INSN) have been inserted. A rising edge indicates the insertion. The controlling circuit should assert the INSACK signal to acknowledge the insertion.
NUMQ NUMD NUMN	Change Available - Indicates the number of quarters (NUMQ), dimes (NUMD) and nickels (NUMN) available for making change (up to 7). If there are more than 7 coins of a type available, then the signal will indicate 7.
BILLSNS	Bill Sense - A high value indicates that a bill is sensed in the bill insertion slot. The controlling circuit should assert BILLIN to feed the bill into the bill tester
BILLOK	Bill OK - A high value indicates that the bill in the bill tester is a valid bill.
CNRET	Coin Return Request - A high value indicates that the user is pressing the coin return lever.
BILLACK	Bill Acknowledge - This signal is asserted to acknowledge a BILLIN or BILLOUT signal.
CHGACK	Change Acknowledge - This signal is asserted to acknowledge a CHGQ, CHGD, CHGN, CHGCOM or RETINS signal.
DISPACK	Dispense Acknowledge - This signal is asserted to acknowledge a DISP signal.
BILLNG	Bill No Good - This signal is asserted to indicate that a fake bill is in the bill tester.

9.3 Timers and One-Shots

Timers and one-shots are devices that operate in real time. To use a timer or one-shot device, open the library manager with the toolbar button and load the "timer" library. You can then locate the desired device in the module list or module hierarchy and drag it onto the main window canvas to create an instance of it.

9.3.1 OSCILLATOR Device

Figure 9.7:
Oscillator

The OSCILLATOR device provides a signal that oscillates at a set frequency in real-world time. You can use it to design circuits such as digital clocks using the LED gates. The default frequency is one hertz. To change the frequency, double click on the OSCILLATOR module to open the

9.3.2 ONESHOT Device

Figure 9.8:
One Shot

9.4 TTL Devices

The TTL device library provides access to a small number of commonly used 7400 series TTL modules. To use this library, open the library manager with the toolbar button and load the "74xx" library. You can then locate the desired device in the module list or module hierarchy and drag it onto the main window canvas to create an instance of it. The supported devices are:

Device	Description
7400	Quad 2-input NAND gates
7402	Quad 2-input NOR gates
7404	Hex Inverters
7408	Quad 2-input AND gates
7410	Tri 3-input NAND gates
7430	8-input NAND gate
7432	Quad 2-input OR gate
7474	Dual D-Latch, edge triggered with clear and preset
7486	Quad 2-input XOR gates
74154	4-16 Decoder
74157	Quad 2-1 Mux
74163	4-bit Synchronous Counter
74175	Quad D-Latch, edge triggered with clear

Please see standard TTL data sheets for a description of these devices.