HD404374FT datasheet(98/161 Pages) RENESAS

98 / 161 page

HD404374/HD404384/HD404389/HD404082/HD404084 Series

Rev.5.00, Sep.11.2003, page 98 of 161

Serial Interface Registers

Serial interface operation setting and serial data reading/writing is controlled by the following registers.

Serial mode register 1 (SMR1: $024)

Serial mode register 2 (SMR2: $025)

Serial data register (SRL: $026, SRU: $027)

Port mode register 3 (PMR3: $00B)

Module standby register 2 (MSR2: $00E)

Serial mode register 1 (SMR1: $024):

Serial mode register 1 (SMR1) has the following functions. See figure 56.

• Serial clock selection

• Prescaler division ratio selection

• Serial interface initialization

The serial mode register 1 (SMR1) is a 4-bit write-only register, and is reset to $0 by an MCU reset.

A write to serial mode register 1 (SMR1) halts the supply of the serial clock to the serial data register (SRL,

SRU) and the octal counter, and resets the octal counter to 000. Therefore, if serial mode register 1

(SMR1) is written to during serial interface operation, data transmission/reception will be suspended and

the serial interrupt request flag (IFS) will be set.

A modification of serial mode register 1 (SMR1) becomes effective after execution of two instructions

following the serial mode register 1 (SMR1) write instruction. The program must therefore provide for the

STS instruction to be executed two cycles after the instruction that writes to serial mode register 1 (SMR1).

HD404374FT Datasheet(PDF) 98 Page - Renesas Technology Corp