UPD78F9222MC(T)-5A4-A NEC, UPD78F9222MC(T)-5A4-A Datasheet - Page 55

• Manufacturer Part Number: UPD78F9222MC(T)-5A4-A
• Description: 8BIT MCU, 4K FLASH, 256B RAM, 78F9222
• Manufacturer: NEC

Specifications of UPD78F9222MC(T)-5A4-A

• Controller Family/series: UPD78
• No. Of I/o's: 17
• Ram Memory Size: 256Byte
• Cpu Speed: 10MHz
• No. Of Timers: 4
• No. Of: RoHS Compliant
• Core Size: 8bit
• Program Memory Size: 4KB
• Oscillator Type: External, Internal

4.2.3
port mode register 4 (PM4). When the P40 to P45 pins are used as an input port, an on-chip pull-up resistor can be
connected in 1-bit units by using pull-up resistor option register 4 (PU4).
Caution Because the P34 pin functions alternately as the RESET pin, if it is used as an input port pin, the
Port 4 is a 6-bit I/O port with an output latch. Each bit of this port can be set to the input or output mode by using
Alternate functions include external interrupt request input, serial interface data I/O, and timer output.
Reset signal generation sets port 4 to the input mode.
Figures 4-6 to 4-9 show the block diagrams of port 4.
Port 4
RD:
function to input an external reset signal to the RESET pin cannot be used. The function of the
port is selected by the option byte. For details, refer to CHAPTER 17 OPTION BYTE.
Also, since the option byte is referenced after the reset release, if low level is input to the RESET
pin before the referencing, then the reset state is not released. When it is used as an input port
pin, connect the pull-up resistor.
Read signal
RD
Reset
Option
Figure 4-5. Block Diagram of P34
byte
CHAPTER 4 PORT FUNCTIONS
User’s Manual U16898EJ5V0UD
P34/RESET
55