M37221M6_03 Datasheet, PDF (46/62 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER with ON-SCREEN DISPLAY CONTROLLER

MITSUBISHI MICROCOMPUTERS
M37221M6-XXXSP
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER
with ON-SCREEN DISPLAY CONTROLLER
(10) Clock for Display
As a clock for display to be used for CRT display, it is possible to
select one of the following 4 types.
• ^{Main clock supplied from the XIN pin}
• ^{Main clock supplied from the XIN pin divided by 1.5}
• ^{Clock from the LC or RC supplied from the pins OSC1 and OSC2.}
• ^{Clock from the ceramic resonator or quartz-crystal oscillator sup-}
plied from the pins OSC1 and OSC2.
This clock for display can be selected for each block by the CRT
clock selection register (address 00ED16).
When selecting the main clock, set the oscillation frequency to
8 MHz.
7
0 0 00 0 0
0
CRT clock selection register
(CK : address 00ED16)
Display clock selection bits
Refer to Table 14.
Fix these bits to “0.”
Fig. 48. Structure of CRT clock selection register
Table 14. Set value of CRT clock selection register and clock for display
b1 b0
Functions
0
0 The clock for display is supplied by connecting RC or LC across the pins OSC1 and OSC2.
0
1
CRT oscillation frequency =
Since the main clock is used as the clock for display, the oscillation frequency is limited. Because _f(XIN)
of this, the character size in width (horizontal) direction is also limited. In this case, pins OSC1
1
0 ^{and OSC2 are also used as input ports P33 and P34 respectively.}
CRT oscillation frequency =
f(XIN)/1.5
The clock for display is supplied by connecting the following across the pins OSC1 and OSC2.
1
1 • a ceramic resonator only for CRT display and a feedback resistor
• a quartz-crystal oscillator only for CRT display and a feedback resistor (Note)
Note: It is necessary to connect other ceramic resonator or quartz-crystal oscillator across the pins XIN and XOUT.
45