UPD75238GJ NEC [NEC], UPD75238GJ Datasheet - Page 80

• Manufacturer Part Number: UPD75238GJ
• Description: 4 BIT SINGLE-CHIP MICROCOMPUTER
• Manufacturer: NEC [NEC]

80
(1) Serial interface (channel 0) functions
(2) Configuration of serial interface (channel 0)
Fig. 4-39 shows the block diagram of the serial interface (channel 0).
The serial interface (channel 0) of the PD75238 has following four different modes.
The functions of the four modes are outlined below.
• Operation halt mode
• Three-wire serial I/O mode
• Two-wire serial I/O mode
• Serial bus interface (SBI) mode
This mode is used when serial transfer is not performed. This mode reduces power consumption.
In this mode, 8-bit data is transferred through three lines: Serial clock (SCK0), serial output (SO0), and
serial input (SI0).
The three-wire serial I/O mode allows full-duplex transmission, so data transfer can be performed at
higher speed.
The user can choose 8-bit data transfer starting with the MSB or LSB, so devices starting with either
the MSB or LSB can be connected.
The three-wire serial I/O mode enables connections to be made with the 75X series, 78K series, and
many other types of peripheral I/O devices.
In this mode, 8-bit data is transferred through two lines: Serial clock (SCK0) and serial data bus (SB0
or SB1). By controlling output levels on the two lines by software, communication with multiple devices
is enabled.
The output levels of SCK0 and SB0 (or SB1) can be controlled by software, so the user can match an
arbitrary transfer format. This means that a line that has been required for handshaking to connect
multiple lines can be eliminated for more efficient I/O port utilization.
In this mode, communication with multiple devices can be performed using two lines: Serial clock
(SCK0) and serial data bus (SB0 or SB1).
This mode conforms to the NEC serial bus format.
In this mode, the sender can output, on the serial data bus, an address for selecting a device subject
to serial communication, commands directed to the remote device, and data. The receiver can identify
an address, commands, and data from received data by hardware. This function enables more efficient
I/O port utilization as in the case of the two-wire serial I/O mode. In addition, this function can simplify
the serial interface control portion of an application program.
PD75238