mc68hc08ln56 Freescale Semiconductor, Inc, mc68hc08ln56 Datasheet - Page 200

• Manufacturer Part Number: mc68hc08ln56
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Liquid Crystal Display Driver (LCD)
should be set to enable the 7-bit programmable divider which is further divided by 4 to control the
reference clock. This allows for a maximum CGMXCLK frequency of approximately 16.6 MHz. See
15-12.
The frame rate bits (FR3:FR0) in the LCD frame rate register (LCDFR) are provided to select an
appropriate frame/field rate. See
15.9 Programming the LCD
The LCD prescaler divider register (LCDDIV) should be set according to the following formula in order to
produce a charge pump frequency of 32.768 kHz.
where CPF is the charge pump frequency, CGMXCLK is the OSC1 (crystal) frequency; PE is the prescale
enable bit in LCDDIV, and DIV is the 7-bit divider.
For example if CGMXCLK = 5.12 MHz, PE should be set and DIV = 39. If CGMXCLK = 32.768 kHz, PE
should be cleared and the DIV bits will be disregarded.
The LCD frame rate register (LCDFR) should be set according to the following formula.
where CGMXCLK is the OSC1 (crystal) frequency; PE is the prescale enable bit in LCDDIV, DIV is the
7-bit divider, and FRAME is the desired frame rate.
Some examples of programmed frame frequencies are listed in
200
For correct operation, program PE and DIV[6:0] bits such that the charge
pump clock is approximately 32.768 KHz for a given CGMXCLK (crystal)
frequency.
CGMXCLK
MC68HC08LN56 • MC68HC708LN56 General Release Specification, Rev. 2.1
Figure 15-12. LCD Frame Frequency Block Diagram
LCDFR
Table
³ DIV[6:0]
³ FR [3:0]
=
-------------------------------------------------------------------------------------------------------------- -
(
(
DIV
DIV 4 PE
15-6.
=
⋅
RND
⋅
÷ 4
NOTE
÷ 2
)
⎛
⎝
BACKPLANE
CGMXCLK
+
-------------------------------- -
CPF 4 PE
CGMXCLK
CLOCK
(
1 PE
1
0
–
SEL
⋅
PE
⋅
BACKPLANE
SELECTS
)
) FRAME 128
÷ 32
⋅
Table
⎞
⎠
15-6.
FIELD
CHARGE PUMP CLOCK
⋅
≈ 32 kHz
÷ 2
FRAME
Freescale Semiconductor
Figure