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LCD Frame Frequency

The LCD controller clock frequency (f

LCD

) can be sourced from either the 32kHz clock or the high-frequency clock divided by 128 as

specified by the LCCS bit. If Stop mode is entered and the 32kHz clock is being used, LCD display operation continues (if OPM = 1).

If Stop mode is entered and the high-frequency clock divided by 128 is being used, the LCD controller is suspended automatically

until Stop mode is exited and the high-frequency clock completes its warmup period.

The bits FRM[3:0] control the generation of the LCD frame frequency from the selected LCD clock source (32kHz or HFClk / 128). The

selected frame frequency (f

FRAME

) is defined as follows.

FRAME

= f

LCD

/ [((FRM[3:0]) + 1) x 96] for 1/3 duty

FRAME

= f

LCD

/ [((FRM[3:0]) + 1) x 64] for static, 1/2, and 1/4 duty

The resulting frame frequency should be between 30Hz and 1000Hz. Example frequencies that can be generated from typical clock

frequencies are shown in Table 31.

LCD Display Memory

The registers LCD0 to LCD16 provide 17 bytes of display memory. Depending on the duty cycle and package type, not all display

memory can be used by the LCD controller. Any display memory that is unused by the LCD controller can be used for application pur-

poses if desired. Tables 32 to 39 show the display memory mapping for different duty cycle and package configurations.

MAXQ Family User’s Guide:

MAXQ2000 Supplement

LCD

= 32,768Hz

LCD

= 7812.5Hz

(1MHz / 128)

LCD

= 38,400Hz

(4.9152MHz / 128)

LCD

= 62,500Hz

(8MHz / 128)

FRM[3:0]

1, 1/2, 1/4 1/3 1, 1/2, 1/4 1/3 1, 1/2, 1/4 1/3 1, 1/2, 1/4 1/3

0 512 341 122 81 600 400 977 651

1 256 171 61 41 300 200 488 326

2 171 114 41 27 200 133 326 217

3 128 85 31 20 150 100 244 163

4 102 68 24 16 120 80 195 130

585572014100 67 163 109

673491712865714093

764431510755012281

8573814 9 6744 109 72

9513412 8 6040 98 65

10 47 31 11 7 55 36 89 59

11 43 28 10 7 50 33 81 54

12 39 26 9 6 46 31 75 50

13 37 24 9 6 43 29 70 47

14 34 23 8 5 40 27 65 43

15 32 21 8 5 38 25 61 41

Table 31. LCD Frame Frequencies (Hz)

Maxim Integrated

1 2 ... 70 71 72 73 74 75 76 77 78 79 80 ... 92 93

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