RA8806
Preliminary Version 1.0
Two Layers Character/Graphic LCD Controller
6-6 Clock and Reset
RA8806 supports internal or external clock source without extra select pin.
6-6-1 OSC Circuit
RA8806 contains a built-in OSC circuits. It generates corresponding clock by connecting an external
4M ~ 12MHz crystal between XG and XD pins. Figure 6-25 is the clock circuit for X’tal oscillator and
external clock.
RA8806
RA8806
XG
XD
XG
XD
CLK
15pF
(4~12MHz)
X’tal
15pF (4~12MHz)
Figure 6-25: Clock Circuit
6-6-2 External Clock
RA8806 can also accept external clock for system clock source. The external clock source can
directly connect to XG pin, and XD pin must be kept floating.
tRCL
tFCL
tWH
EXT￠0
tWL
tC
Figure 6-26 : External Clock
Table 6-18 : Clock Timing
VDD = 5V
Ta = –20 to 75℃
VDD = 3.3V
Min. Max.
10
10
Signal
Symbol
Parameter
Unit Condition
Min.
Max.
External clock rise time
External clock fall time
tRCL
tFCL
—
10
—
ns
ns
—
10
—
External clock
HIGH-level pulse width
External clock
LOW-level pulse width
tWH
Note 1. Note 2. Note 1. Note 2.
Note 1. Note 2. Note 1. Note 2.
ns
EXT Φ0
tWL
tC
ns
ns
External clock period
66.6
—
83.3
—
Notes:
475
1. (tC − tRCL − tFCL ) ×
2. (tC − tRCL − tFCL ) ×
< tWH ,tWL
1000
525
> tWH ,tWL
1000
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