HD4074329S Renesas Electronics America, HD4074329S Datasheet - Page 70

• Manufacturer Part Number: HD4074329S
• Description: MCU 4-Bit HMCS400 CISC 20KB EPROM 3.3V/5V 64-Pin SDIP
• Manufacturer: Renesas Electronics America

Specifications of HD4074329S

• Package: 64SDIP
• Family Name: HMCS400
• Maximum Speed: 4.5 MHz
• Ram Size: 268 Byte
• Program Memory Size: 20 KB
• Operating Supply Voltage: 3.3|5 V
• Data Bus Width: 4 Bit
• Program Memory Type: EPROM
• Number Of Programmable I/os: 35
• On-chip Adc: 4-chx8-bit
• Operating Temperature: -20 to 75 °C
• Number Of Timers: 3

HD404328 Series
Zero-Crossing Detection Circuit
The MCU has a zero-crossing detection circuit that generates a digital signal in synchronism with an AC
signal input to the ZCD pin through an external capacitor. A block diagram of the zero-crossing detection
circuit is shown in figure 41.
The zero-crossing detection circuit has two modes (low sensitivity mode and high sensitivity mode) which
are set by port mode register B (PMRB: $011) as shown in table 33.
A digital signal generated by the zero-crossing detection circuit sets the zero-crossing interrupt request flag
(IFZC). The interrupt edge is selected by the interrupt mode register (IMR: $010). This signal can be
made as the input clock of timer B by setting the input clock source of timer mode register B (TMB: $009)
for external event input.
Note: After MCU reset, the D
Table 33
PMRB
1
0
1
Note: * Becomes low sensitivity in subactive mode.
66
current) always flows because a bias circuit within the zero-crossing circuit is still operating. This
current flows in all MCU operation modes, but it is particularly critical in stop mode because the
MCU is more affected by bias current since the other circuits of the LSI are not dissipating much
current. If the zero-crossing detection function is not being used, use port mode register B to set
this pin to D
AC input
signal
Port Mode Register B
0
0
1
0
1
External
capacitor
8
Figure 41 Block Diagram of Zero-Crossing Detection Circuit
EVENT pin
D
or EVENT. This prevents the bias current from flowing.
8
/ZCD/
Port Selection
ZCD (low sensitivity mode)
ZCD (high sensitivity mode)*
D
EVENT
8
8
MPX
/ZCD/EVENT pin is set to ZCD. With this setting, a supply current (bias
Zero-crossing
detection circuit
Port mode register B
MPX
2
MPX
Interrupt mode register
MPX
2
D
EVENT
(Refer to
figure 27.)
8
port input
IFZC