NEC 78014Y Series, User Manual

Page: 321 / 547

www.DataSheet4U.com
CHAPTER 16 SERIAL INTERFACE CHANNEL 0 (
µ
PD78014Y Subseries)
321
16.1 Serial Interface Channel 0 Functions
Serial interface channel 0 employs the following five modes.
• Operation stop mode
• 3-wire serial I/O mode
• SBI (Serial bus interface) mode
• 2-wire serial I/O mode
• I
2
C (Inter IC) bus mode
Caution Do not switch the operation mode (3-wire serial I/O/2-wire serial I/O/SBI/I
2
C bus) during the serial
interface channel 0 operation enable. The operation mode should be switched after stopping the
serial operation.
(1) Operation stop mode
Operation stop mode is used when serial transfer is not performed, thus reducing power dissipation.
(2) 3-wire serial I/O mode (MSB/LSB-first switchable)
3-wire serial I/O mode transfers 8-bit data with three lines; serial clock (SCK0), serial output (SO0), and serial
input (SI0).
3-wire serial I/O mode can transfer/receive at the same time, so the data transfer processing time is fast.
The start bit of 8-bit data to undergo serial transfer is switchable between MSB and LSB, so it is possible to connect
devices of any start bit.
3-wire serial I/O mode is valid for connection of peripheral I/O units and display controllers which incorporate
a conventional synchronous clocked serial interface as is the case with the 75X/XL, 78K and 17K series.
(3) SBI (serial bus interface) mode (MSB first)
This mode is used for 8-bit data transfer with two or more devices using two lines of serial clock (SCK0) and serial
data bus (SB0 or SB1) (see Figure 16-1).
The SBI mode complies with the NEC serial bus format and distinguishes the transfer data into “address”,
“command”, and “data” to transmit or receive the data.
• Address : Data to select objective devices in serial communication
• Command : Data to instruct objective devices
• Data : Data to be actually transferred
In the actual transfer, the master device first outputs the “address” to the serial bus, and selects the slave device
as communication target from among two or more devices. The serial transfer is then performed by transmitting
and receiving “command” and “data” between the master and slave devices. The receiver automatically
distinguishes the received data as “address”, “command”, or “data”, by hardware.
This function enables to use input/output ports effectively and to simplify a serial interface controller of application
programs.
In addition, the wake-up function for handshake, and the acknowledge signal and busy signal output function
can be used.