38B5 Group User’s Manual
1-67
HARDWARE
MASK OPTION OF PULL-DOWN RESISTOR
(object product: M38B5XMXH-XXXFP)
Whether built-in pull-down resistors are connected or not to high-
breakdown voltage ports P2
0
to P2
7
and P8
0
to P8
3
can be specified
in ordering mask ROM. The option type can be specified from among
8 types; A to G, P as shown Table 12.
Table 12 Mask option type of pull-down resistor
Connective port of pull-down resistor
(connected at “1” writing)
P2
0
P2
1
P2
2
P2
3
P2
4
P2
5
P2
6
P2
7
P8
0
P8
1
P8
2
P8
3
A ($41)
B ($42)
C ($43)
D ($44)
E ($45)
F ($46)
G ($47)
P ($50)
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Notes 1:
The electrical characteristics of high-breakdown voltage ports
P2
0
to P2
7
and P8
0
to P8
3
’s built-in pull-down resistors are the
same as that of high-breakdown voltage ports P0
0
to P0
7
.
2:
The absolute maximum ratings of power dissipation may be
exceed owing to the number of built-in pull-down resistor. After
calculating the power dissipation, specify the option type.
3:
One time PROM version and EPROM version cannot be
specified whether built-in pull-down resistors are connected or not
likewise option type A.
4:
INT
3
function and CNTR
1
function cannot be used in the option
type P.
Power Dissipation Calculating Method
G
Fixed number depending on microcomputer’s standard
V
OH
output fall voltage of high-breakdown port
2 V (max.); | Current value | = at 18 mA
Resistor value 43 V / 900
μ
A = 48 k
(min.)
Power dissipation of internal circuit (CPU, ROM, RAM etc.) = 5 V
15 mA = 75 mW
G
Fixed number depending on use condition
Apply voltage to V
EE
pin: Vcc – 45 V
Timing number a; digit number b; segment number c
Ratio of Toff time corresponding Tdisp time: 1/16
Turn ON segment number during repeat cycle: d
All segment number during repeat cycle: c (= a
c)
Total number of built-in resistor: for digit; f, for segment; g
Digit pin current value h (mA)
Segment pin current value i (mA)
(1) Digit pin power dissipation
{h
b
(1–Toff/Tdisp)
voltage} / a
(2) Segment pin power dissipation
{i
d
(1–Toff/Tdisp)
voltage} / a
(3) Pull-down resistor power dissipation (digit)
{power dissipation per 1 digit
(b
f / b)
(1–Toff/Tdisp) } / a
(4) Pull-down resistor power dissipation (segment)
{
power dissipation per 1 segment
(d
g / c)
(1–Toff/Tdisp) } / a
(5)
Internal circuit power dissipation (CPU, ROM, RAM etc.) = 75 mW
(1) + (2)+ (3) + (4) + (5) = X mW
Power Dissipation Calculating example 1
G
Fixed number depending on microcomputer’s standard
V
OH
output fall voltage of high-breakdown port
2 V (max.); | Current value | = at 18 mA
Resistor value 43 V / 900
μ
A = 48 k
(min.)
Power dissipation of internal circuit (CPU, ROM, RAM etc.) = 5 V
15 mA = 75 mW
G
Fixed number depending on use condition
Apply voltage to V
EE
pin: Vcc – 45 V
Timing number 17; digit number 16; segment number 20
Ratio of Toff time corresponding Tdisp time: 1/16
Turn ON segment number during repeat cycle: 31
All segment number during repeat cycle: 340 (= 17
20)
Total number of built-in resistor: for digit; 16, for segment; 20
Digit pin current value: 18 (mA)
Segment pin current value: 3 (mA)
(1) Digit pin power dissipation
{18
16
(1–1/16)
2} / 17 = 31.77 mW
(2) Segment pin power dissipation
{3
31
(1–1/16)
2} / 17 = 10.26 mW
(3) Pull-down resistor power dissipation (digit)
(45 – 2)
2
/48
(16
16/16)
(1 – 1/16) / 17 = 33.99 mW
(4) Pull-down resistor power dissipation (segment)
(45 – 2)
2
/48
(31
20/20)
(1 – 1/16) / 17 = 65.86 mW
(5)
Internal circuit power dissipation (CPU, ROM, RAM etc.) = 75 mW
(1) + (2)+ (3) + (4) + (5) = 217 mW
Fig. 76 Digit timing waveform (1)
MASK OPTION OF PULL-DOWN RESISTOR
D
I
G
0
D
I
G
1
D
I
G
2
D
I
G
3
D
I
G
1
4
D
I
G
1
5
D
I
G
1
6
T
i
m
i
n
g
n
u
m
b
e
r
1
2
3
1
6
1
7
1
5
1
4
T
s
c
a
n
R
e
p
e
a
t
c
y
c
l
e
Option
type
Restriction
(Note 4)