Control Registers - NEC UPD703116 User Manual

32-bit single-chip microcontrollers

Table of Contents

10.2.3 Control registers

(1) Asynchronous serial interface mode register 0 (ASIM0)

The ASIM0 register is an 8-bit register that controls the UART0 transfer operation.

This register can be read/written in 8-bit or 1-bit units.

Cautions 1. When using UART0, be sure to set the external pins related to the UART0 function to the

control mode before setting clock selection register 0 (CKSR0) and baud rate generator

control register 0 (BRGC0), and then set the UARTCAE0 bit to 1. Then set the other bits.

2. Set the UARTCAE0 and RXE0 bits to 1 while a high level is input to the RXD0 pin. If

these bits are set to 1 while a low high level is input to the RXD0 pin, reception will be

Bit position

Note Only the ASIS0, ASIF0, and RXB0 registers are reset.

CHAPTER 10 SERIAL INTERFACE FUNCTION

Controls the operating clock.

0: Stops clock supply to UART0.

1: Supplies clock to UART0.

Cautions 1. When UARTCAE0 = 0 is set, UART0 is asynchronously reset

2. When UARTCAE0 = 0, UART0 is in a reset state. To operate

UART0, first set UARTCAE0 = 1.

3. When the UARTCAE0 bit is cleared from 1 to 0, all the registers

of UART0 are initialized. When setting UARTCAE0 = 1 again, be

sure to re-set the registers of UART0.

The output of the TXD0 pin goes high when transmission is disabled, regardless of

the setting of the UARTCAE0 bit.

Enables/disables transmission.

0: Disable transmission

1: Enable transmission

Cautions 1. Set the TXE0 bit to 1 after setting the UARTCAE0 bit to 1 at

startup. Set the UARTCAE0 bit to 0 after setting the TXE0 bit to

2. To initialize the transmission unit, clear (0) the TXE0 bit, and

after letting 2 cycles of the base clock elapse, set (1) the TXE0

bit again. If the TXE0 bit is not set again, initialization may not

be successful (for details about the base clock, refer to 10.2.6

(1) (a) Base clock).

User's Manual U14492EJ5V0UD

Initial value