AD6426 Analog Devices, AD6426 Datasheet - Page 19

• Manufacturer Part Number: AD6426
• Description: Enhanced GSM Processor
• Manufacturer: Analog Devices

Keypad / Backlight / Display Interface
This interface combines all functions of display and keyboard
as shown in Table 10.
By providing 4 keypad-column outputs (open drain, pull low)
and 6 keypad-row inputs the AD6426 can monitor up to 24
keys. Additionally, an extra column can be implemented by
using the “ghost column” method for a total of 30 keys. The
H8 processor is interrupted whenever a key is pressed. The
KEYPADCOL pins are connected to the Keypad Column3-0
flags in the KEYPAD COLUMN CC Control Register 9.
The six KEYPADROW pins are connected to the Keypad Row
5-0 flags in the KEYPADROW CC Control Register 10.
One backlight control output (BACKLIGHT) is provided,
which can be modulated to provide the same perceived
brightness for a reduced average current. Switching frequency
as well as duty cycle can be modified to compensate for
ambient lighting levels and changing battery voltage.
The BACKLIGHT output is activated by setting the
Backlight1 flag in the SYSTEM CC Control Register 0.
Once activated, an internal PWM circuit can control the
frequency and the duty cycle of the output signal. The PWM
circuit is enabled by the Modulate1 flag in the BACKLIGHT
CC Control Register 50. To switch the backlight continuously
on, enable the Backlight 1 flag and disable the Modulate 1
flag.
This Information applies to a product under development. Its characteristics and specifications are subject to change without notice. Analog Devices assumes no
obligation regarding future manufacture unless otherwise agreed to in writing. No responsibility is assumed by Analog Devices for its use; nor for any
infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent
rights of Analog Devices.
Revision Preliminary 2.3 (June 9, ´98)
Preliminary Technical Information
Name
KEYPADROW5 : 0
KEYPADCOL3 : 0
BACKLIGHT
DISPLAYCS
LCDCTL
GPIO3
GPIO4
3 : 0
5 : 0
Bit
Bit
Bit
5
Table 10. Keypad / Backlight / Display Interface
KEYPAD COLUMN CC Control Register 9
Keypad Column 3-0
KEYPADROW CC Control Register 10
Keypad Row 5-0
SYSTEM CC Control Register 0
Backlight 1
I/O
O
O
O
O
O
O
I
Function
Keypad row inputs
Keypad column strobes
Backlight control
Display Controller chip
select
LCD Control / Serial Display
Data Output
Serial Display Data Output
Serial Display Clock Output
- 19 -
The frequency is determined by the flags Backlight LED
Control (1:0) in the same register as shown in Table 11.
Duty cycle can be selected between 0 and 124/128 in 32 steps
of 4/128 by programming the Backlight Duty Cycle (4:0) flags
in the POWER CONTROL INTERNAL CC Control Register
44.
The active period is determined according to the formula:
The 6426 offers both parallel and serial interfaces for
connecting to LCD display controllers.
The parallel interface to a LCD controller is provided by two
dedicated control signals (LCDCTL and DISPLAYCS) and
parts of the address and data bus. A typical interface is shown
in Figure 5.
The on-chip control circuit automatically generates wait states
for interfacing to external display devices.
7 : 3
1: 0
Bit
Bit
2
Active (high) Period =
BACKLIGHT CC Control Register 50
Modulate 1
Backlight LED Control (1:0)
POWER CONTROL INTERNAL CC Control
Register 44
Backlight Duty Cycle (4:0)
Figure 5. Parallel Display Interface
AD6426
Bit 1
Table 11. Backlight Frequency
DISPLAYCS
DATA (15:8)
0
0
1
1
LCDCTL
ADD(0)
HWR
Bit 0
0
1
0
1
Backlight Duty Cycle (4:0) × 4
Confidential Information
6.3475 kHz
12.695 kHz
25.390 kHz
50.780 kHz
Frequency
DATA (7:0)
R/W
E
RS
CS
Controller
LCD
128
AD6426