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 P20 to P27 and P80 to P83 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
A ($41)
B ($42)
C ($43)
D ($44)
E ($45)
F ($46)
G ($47)
Connective port of pull-down resistor
(connected at “1” writing)
P20 P21 P22 P23 P24 P25 P26 P27 P80 P81 P82 P83
1
11
1
Notes 1: The electrical characteristics of high-breakdown voltage ports
P20 to P27 and P80 to P83’s built-in pull-down resistors are the
same as that of high-breakdown voltage ports P00 to P07.
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: INT3 function and CNTR1 function cannot be used in the option
type P.
Power Dissipation Calculating Method
q Fixed number depending on microcomputer’s standard
VOH output fall voltage of high-breakdown port
2 V (max.); | Current value | = at 18 mA
Resistor value 43 V / 900
A = 48 k (min.)
Power dissipation of internal circuit (CPU, ROM, RAM etc.) = 5 V !
15 mA = 75 mW
q Fixed number depending on use condition
Apply voltage to VEE 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
q Fixed number depending on microcomputer’s standard
VOH output fall voltage of high-breakdown port
2 V (max.); | Current value | = at 18 mA
Resistor value 43 V / 900
A = 48 k (min.)
Power dissipation of internal circuit (CPU, ROM, RAM etc.) = 5 V !
15 mA = 75 mW
q Fixed number depending on use condition
Apply voltage to VEE 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
DIG0
DIG1
DIG2
DIG3
DIG14
DIG15
DIG16
Timing number
12
3
1617
15
14
Tscan
Repeat cycle
Option
type
Restriction
P ($50)
1
11
(Note 4)