M38203M4 Datasheet, PDF (256/344 Pages) Mitsubishi Electric Semiconductor – 8-BIT SINGLE-CHIP MICROCOMPUTER

APPLICATION
2.7 LCD drive control circuit
(3) Control procedure
Figure 2.7.13 shows the setting of related registers to turn on all the LCD display in Figure 2.7.10,
and Figure 2.7.14 shows the control procedure.
Specifications: •Frame frequency = 122 Hz
•Duty ratio number = 4, Bias value = 1/3
•Segment output; SEG0 to SEG13 are used.
•Ports P0 and P1 are set as I/O ports, port P3 is set as input port.
b7
b0
0 0 0 0 0 0 0 0 _{SEG: Segment output enable register [Address 3816]}
b0: Segment output enable bit 0
0: Input ports P30–P37
b1: Segment output enable bit 1
0: I/O ports P00, P01
b2: Segment output enable bit 2
0: I/O ports P02–P07
b3: Segment output enable bit 3
0: I/O ports P10, P11
b4: Segment output enable bit 4
0: I/O port P12
b5: Segment output enable bit 5
0: I/O ports P13–P17
b7, b6: Fix these bits to “0”
b7
b0
1 0 1 0 0 0 1 1 _{LM: LCD mode register [Address 3916]}
b1, b0: Duty ratio selection bits
b1b0
11: 4 (use COM0–COM3)
b2: Bias control bit
0: 1/3 bias
b3: LCD enable bit
0: LCD OFF (after setting data into
the RAM for LCD display, turn on)
b4: Fix this bit to “0”
b6, b5: LCD circuit divider division ratio selection bits
b6b5
01: 2 division of LCDCK count source V
b7: LCDCK count source selection bit
1: f(XIN)/8192 V
V: •f(LCDCK) = Count source frequency for LCDCK/LCD circuit division ratio
•Frame frequency = f(LCDCK)/duty ratio number
From the above, the frame frequency at f(XIN) = 8 MHz is as follows:
Frame frequency f =
8 ! 10⁶
1
8192 ^! 2
!
1
4
≈ 122.070 Hz
Fig. 2.7.13 Setting of related registers
2–170
3820 GROUP USER’S MANUAL