NEC 78014Y Series, User Manual

Page: 264 / 547

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CHAPTER 15 SERIAL INTERFACE CHANNEL 0 (
µ
PD78014 Subseries)
264
15.1 Serial Interface Channel 0 Functions
Serial interface channel 0 employs the following four modes.
• Operation stop mode
• 3-wire serial I/O mode
• SBI (serial bus interface) mode
• 2-wire serial I/O mode
Caution Do not switch the operation mode (3-wire serial I/O/2-wire serial I/O/SBI) during the serial interface
channel 0 operation enable. The operation mode should be switched after stopping the serial
operation.
(1) Operation stop mode
This mode is used when serial transfer is not carried out. Power dissipation can be reduced.
(2) 3-wire serial I/O mode (MSB-/LSB-first selectable)
This mode is used to 8-bit data transfer using three lines, one each for serial clock (SCK0), serial output (SO0)
and serial input (SI0).
This mode enables simultaneous transmission/reception and therefore reduces the data transfer processing time.
The start bit of transferred 8-bit data is switchable between MSB and LSB, so that devices can be connected
regardless of their start bit recognition.
This mode should be used when connecting with peripheral I/O devices or 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 15-1).
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 into “address”, “command”, or “data”, by hardware.
This function enable to use input/output ports effectively and to simplify a serial interface controller of application
programs.
In addition, wake-up function for handshake, acknowledge signal, and busy signal output function can be used.