Digilent DIO2 - Manual (Page 6)

Digilab DIO2 Reference Manual Digilent, Inc.
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Parameter Symbol Min Max Unit Test Pin
Enable cycle time tc 500 ns E
Enable High pulse width tw 220 ns E
Enable rise/fall time tr, tf 25 ns E
RS, R/W setup time tsu 40 ns RS, R/W
RS, R/W hold time th 10 ns RS, R/W
Read data output delay tD 60 120 ns DB0-DB7
Read data hold time tDH 20 ns DB0-DB7
Write data setup time tsu1 40 ns DB0-DB7
Write data hold time th1 10 ns DB0-DB7
LCD start-up sequence
The manufacturer requires that a startup sequence with specific timings be
followed to ensure proper LCD operation. After power-on, at least 20ms
must elapse before the function-set instruction code can be written to set the
bus width, number of lines, and character patterns (8-bit interface, 2 lines,
and 5x8 dots are appropriate). After the function-set instruction, at least
37us must elapse before the display-control instruction can be written (to
turn the display on, turn the cursor on or off, and set the cursor to blink or
no blink). Then after another 37us, the display-clear instruction can be
issued, followed by a 1.52ms delay. Finally, the entry-mode instruction code
can be used to set address increment (or address decrement) mode, and
display shift mode (on or off). Once this sequence is complete, data can be
written into the DDRAM to cause information to appear on the display.
LEDs
Sixteen individual LEDs (8 red, 4 yellow, and 4 green) are provided for
circuit outputs. The LED cathodes are driven directly from the CPLD, and
the anodes are tied to Vdd via 270-ohm resistors (so the LED drive signals
are active low). When the CPLD is configured with the code shown in the
appendix, two 8-bit registers at locations x04 and x05 drive the LED
cathode signals. Note the LED signals are inverted in the VHDL code, so a
logic “1” turns on the LEDs.
Seven-segment LED display
The DIO2 board contains a modular 4-digit, common anode, seven-segment LED display. In a
common anode display, the seven anodes of the LEDs forming each digit are connected to four
common circuit nodes (labeled AN1 through AN4 on the DIO2 board). Each anode, and therefore each
digit, can be independently turned on and off by driving these signals to a ‘1’ or a ‘0’. The cathodes of
Wait for 20ms
Power On
Function Set
Wait for 37us
Display Control Set
Wait for 37us
Display Clear
Wait for 1.52ms
OK for operations
LCD startup sequence