UPD78F9222MC(T)-5A4-A NEC, UPD78F9222MC(T)-5A4-A Datasheet - Page 60

• 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

4.2.4
port mode register 12 (PM12). When the P123 pin is used as an input port, an on-chip pull-up resistor can be
connected by using pull-up resistor option register 12 (PU12).
P121 and P122 pins differ, therefore, depending on the selected system clock oscillator. The following three system
clock oscillators can be used.
(1) High-speed internal oscillator
(2) Crystal/ceramic oscillator
(3) External clock input
60
Port 12 is a 3-bit I/O port with an output latch. Each bit of this port can be set to the input or output mode by using
The P121 and P122 pins are also used as the X1 and X2 pins of the system clock oscillator. The functions of the
The system clock oscillation is selected by the option byte. For details, refer to CHAPTER 17 OPTION BYTE.
Reset signal generation sets port 12 to the input mode.
Figures 4-10 and 4-11 show the block diagrams of port 12.
The P121 and P122 pins can be used as I/O port pins.
The P121 and P122 pins cannot be used as I/O port pins because they are used as the X1 and X2 pins.
The P121 pin is used as the X1 pin to input an external clock, and therefore it cannot be used as an I/O port pin.
The P122 pin can be used as an I/O port pin.
Port 12
P12:
PM12:
RD:
WR××: Write signal
WR
WR
RD
Port register 12
Port mode register 12
Read signal
PORT
PM
PM121, PM122
(P121, P122)
Output latch
Figure 4-10. Block Diagram of P121 and P122
PM12
P12
CHAPTER 4 PORT FUNCTIONS
User’s Manual U16898EJ5V0UD
P121/X1,
P122/X2