UPD75518 NEC, UPD75518 Datasheet - Page 84

• Manufacturer Part Number: UPD75518
• Description: 4 BIT SINGLE-CHIP MICROCOMPUTER
• Manufacturer: NEC

84
4.8.1 Serial Interface (Channel 0) Functions
• Operation halt mode
• Three-wire serial I/O mode
• Two-wire serial I/O mode
• Serial bus interface (SBI) mode
4.8.2 Configuration of Serial Interface (Channel 0)
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 transmitter 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.
The clock synchronous 8-bit serial interface is contained in the PD75518(A) and has four modes.
The functions of the four modes are outlined below.
This mode is used when serial transfer is not performed. This mode reduces power consumption.
Fig. 4-34 shows the block diagram of the serial interface (channel 0).
PD75518(A)