¡ Semiconductor

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MSM6794

Original Oscillation Frequency and Frame Frequency

Frame frequency calculation

For 1/33, 1/44, 1/48 DUTY:

(Original oscillation clock cycle) ¥ (1/frequency dividing ratio) ¥ 4224 = frame cycle

................ Formula 1

For 1/41 DUTY:

(Original oscillation clock cycle) ¥ (1/frequency dividing ratio) ¥ 4264 = frame cycle

................ Formula 2

Frame frequency can be calculated by the above formulas.

Example 1) For original oscillation 350 [kHz], frequency dividing ratio 1/1, and 1/33 duty

specification:

Therefore, frame frequency = 82.9 [Hz]

Example 2) For original oscillation 1 [MHz], frequency dividing ratio 1/3, 1/41 duty specification:

Therefore, frame frequency = 78.2 [Hz]

Original oscillation frequency and BUSY time

When RAM data is written or read, data processing time (BUSY time) occurs. BUSY time is a

maximum of [(original oscillation clock cycle) ¥ 8]. As the original oscillation frequency

increases, BUSY time becomes shorter (not influenced by the frequency dividing ratio).

By increasing the original oscillation frequency, BUSY time can be made shorter in proportion.

In this case frame frequency also increases. So, set the frequency dividing ratio so that frame

frequency reaches a frequency close to the frame frequency to be used.