
CHAPTER 2 PIN FUNCTIONS
User’s Manual U12768EJ4V1UD
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(12) P120 (Port 12) 3-state I/O
P120 is a 1-bit I/O port that can be set to input or output in 1-bit units. P120 can also function as a control signal
(WAIT) pin when a wait is inserted in the bus cycle.
(a)
Port function
P120 can be set to input or output using the port 12 mode register (PM12).
(b) Alternate functions
(i)
WAIT (Wait) input
This is an input pin for the control signal used to insert waits into the bus cycle. This pin is sampled at
the falling edge of the clock during the T2 or TW state of the bus cycle.
(13) CLKOUT (Clock out) output
This is the pin used to output the bus clock generated internally.
(14) RESET (Reset) input
The RESET pin is an asynchronous input and inputs a signal that has a constant low level width regardless of the
status of the operating clock. When this signal is input, a system reset is executed as the first priority ahead of all
other operations.
In addition to being used for ordinary initialization/start operations, this pin can also be used to release a standby
mode (HALT, IDLE, or software STOP mode).
(15) X1 and X2 (Crystal)
These pins are used to connect the resonator that generates the main clock.
These pins can also be used to input an external clock. When inputting an external clock, connect the X1 pin and
leave the X2 pin open.
(16) XT2 (Crystal for subclock)
This pin is used to connect the resonator that generates the subclock.
(17) AVDD (Power supply for analog)
This is the analog positive power supply pin for the A/D converter. Be sure to keep the same potential as the VDD
pin.
(18) AVSS (Ground for analog)
This is the ground pin for the A/D converter.
(19) AVREF (Analog reference voltage) … input
This is the reference voltage supply pin for the A/D converter. Be sure to keep the same potential as the AVDD
pin.
(20) BVDD (Power supply for bus interface)
This is the positive power supply pin for the bus interface and its alternate-function port. Be sure to keep the
same potential as the VDD pin.
(21) BVSS (Ground for bus interface)
This is the ground pin for the bus interface and its alternate-function port.