Display And Keypad, Detailed Description - Motorola MTP700 Detailed Service Manual

TRANSCEIVER 800 MHz

Display and Keypad, Detailed Description

Display
The LCD (Liquid Crystal Display) Module is a Graphic Display based upon the
KS0741TB-01 display driver.
It consist of LCD Holographic Glass, LED backlight and a 22 pin flex cable connected to
the Keypad board.
The Communication to the RedCap2 IC is performed using a SPI protocol (Serial Periph-
eral Interface). The Operation of the LCD is determined upon the RS line configuration
(Data/Command).
The Display is 128 X 100 (Columns X Rows respectively).
Keypad
The RedCap2 processor (RCE) is responsible for decoding key presses and displaying
them properly on the LCD. The keys are arranged into a matrix of five rows and five col-
umns, which includes the Volume and PTT keys.
The PWR key is not decoded by the RCE; it directly drives the GCAP3, which sends a
signal to RCE through INT1. The five row lines are pulled high via five internal 22 Kohm
resistors. The five row lines and five column lines are fed to RedCap2 I/O pins. Pressing
any key also generates the keypad internal interrupt. The RedCap2 debounces the keys
by reading them 25 milliseconds later.
The keypad-decoding scheme works as follows:
1. RedCap2 sets rows to inputs; all columns are set as outputs and driven logic low.
2. Rows are pulled logic high. When a key is pressed, one row goes low, which indicates
3. RedCap2 reads rows. A low on that row indicates a key press. All others are high.
4. RedCap2 sets all columns to output logic high.
5. One column at a time is set to output logic low. RedCap2 reads the columns to see
6. The low row level (in step 3) and low column level (in step 5) indicate the correct col-
All keypad circuitry is located on the keypad board. Refer to the keypad board schemat-
ics.
MTP700 Portable Radio / Detailed Service Manual
a key press and sends an internal interrupt.
which one is now at a logic low level.
umn and row.
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