
TS-7250 MANUAL
CONNECTORS AND HEADERS
5.8 LCD Header
The LCD Port can be used to interface to a standard alphanumeric LCD display or as 11
additional digital I/O lines. The header has been arranged to allow a 14-pin ribbon cable to
directly connect to industry standard LCD displays.
Table: LCD Header Pin Configuration
GND
Bias
LCD_WR
LCD_0
LCD_2
LCD_4
LCD_6
2
4
6
8
10
12
14
1
3
5
7
9
11
13
5V
LCD_RS
LCD_EN
LCD_1
LCD_3
LCD_5
LCD_7
Technologic Systems has a 2x24 LCD display available with software drivers for rapid
development.
DIO lines LCD_0 thru LCD_7 are a byte-wide port using Port A on the EP9302 and are
accessed via the data register at physical address location
0x8084_0000
. The DDR for
this port is at
0x8084_0010
. Because this port is interfacing to a 5V LCD, 1.0K Ohm
resistors have been added in series between the EP9302 and the LCD_0 thru LCD_7
pins. This is required since the LCD data bus could be driving these lines above 3.3V. The
series resistors prevent the LCD from overdriving the EP9302 Port A pins.
If using these pins for general purpose DIO, the current sourcing and sinking capability of
these DIO pins is limited by the 1.0K Ohm resistors.
LCD_EN, LCD_RS, and LCD_WR are DIO pins using EP9302 Port H bits 3 through 5
respectively and are accessed via the data register at physical address location
0x8084_0040
. The DDR for this port is at
0x8084_0044
. When these DIO pins are
configured as outputs, they can source 4 mA or sink 8 mA and have logic swings between
3.3V and ground. When configured as inputs, they have standard TTL level thresholds
and must not be driven below 0 Volts or above 3.3 Volts. These DIO pins have 100K Ohm
bias resistors biasing these inputs to a logic “1”. It is important not to change the other bit
positions in these Port H registers since the other DIO pins are being used on the
TS-
7250
. All accesses to these registers should use read-modify-write cycles.
Pin 4 on this header (labeled Bias) is a 620 Ohm resistor to ground for LCD contrast
biasing. The 5V power on the LCD header has a 750 mA Poly-Fuse to limit the current.
!
Warning
LCD pins 3, 5, and 6 use 0-3.3V logic levels. Do not drive these lines to 5V.
LCD Interface
A 14-pin LCD connector is provided for interfacing with standard alphanumeric LCD
displays. These displays use a common controller, the Hitachi HD44780 or equivalent.
While software written for the HD44780 works with all displays using the controller, the
cable needed is dependent on the display used.
For most displays, a straight-through type ribbon cable can be used. The connector on the
LCD display is typically mounted on the backside of the display.
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