38B7 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
PRELIMINARY
Notice: This is not a final specification.
change.
Some parametric limits are subject to
54
Timing Setting
Each timing is set by the FLDC mode register, Tdisp time set reg-
ister, Toff1 time set register, and Toff2 time set register.
(1) Tdisp time setting
The Tdisp time means the length of display timing. In non-grada-
tion display mode, it consists of the FLD display output term and
the Toff1 time. In gradation display mode, it consists of the display
output term and the Toff1 time plus a low signal output term for
dark display. Set the Tdisp time by the Tdisp counter count source
selection bit of the FLDC mode register and the Tdisp time set
register. Supposing that the value of the Tdisp time set register is
n, the Tdisp time is represented as Tdisp = (n+1)
t (t: count
source). When the Tdisp counter count source selection bit of the
FLDC mode register is “0” and the value of the Tdisp time set reg-
ister is 200 (C8
16
), the Tdisp time is: Tdisp = (200 + 1)
4.0
μ
s (at
X
IN
= 4 MHz) = 804
μ
s. When reading the Tdisp time set register,
the counting value is read out.
(2) Toff1 time setting
The Toff1 time means a non-output (low signal output) time to pre-
vent blurring of FLD and for dimmer display. Use the Toff1 time set
register to set this Toff1 time. Make sure the value set to Toff1 is
smaller than Tdisp and Toff2. Supposing that the value of the Toff1
time set register is n1, the Toff1 time is represented as Toff1 =
n1
t. When the Tdisp counter count source selection bit of the
FLDC mode register is “0” and the value of the Toff1 time set reg-
ister is 30 (1E
16
), Toff1 = 30
4.0
μ
s (at X
IN
= 4 MHz) = 120
μ
s.
Be sure to set the value of 03
16
or more to the Toff1 time set reg-
ister (address 0EF6
16
).
(3) Toff2 time setting
The Toff2 time is time for dark display. For bright display, the FLD
display output remains effective until the counter that is counting
Tdisp underflows. For dark display, however, “L” (or “off”) signal is
output when the counter that is counting Toff2 underflows. This
Toff2 time setting is valid only for FLD ports which are in the gra-
dation display mode and whose gradation display control RAM
value is “1” .
Set the Toff2 time by the Toff2 time set register. Make sure the
value set to Toff2 is smaller than Tdisp but larger than Toff1. Sup-
posing that the value of the Toff2 time set register is n2, the Toff2
time is represented as Toff2 = n2
t. When the Tdisp counter
count source selection bit of the FLDC mode register is “0” and
the value of the Toff2 time set register is 180 (B4
16
), Toff2 = 180
4.0
μ
s (at X
IN
= 4 MHz) = 720
μ
s.
When bit 7 of the FLD output control register (address 0EFC
16
) is
set to “1”, be sure to set the value of 03
16
or more to the Toff2 time
set register (address 0EF7
16
).
Fig. 54 FLD and digit output timing
Toff1
T
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s
p
T
o
f
f
1
T
o
f
f
2
Tdisp
Gradation display mode is not selected
(Address 0EF4
16
bit 5 = “0”)
Gradation display mode is selected and set for bright display
(Address 0EF4
16
bit 5 = “1” and the corresponding gradation
display control data = “0”)
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Low output term for
blurring prevention
Gradation display mode is selected and set for dark display
(Address 0EF4
16
bit 5 = “1” and the corresponding gradation
display control data = “1”)
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