RS5C348_REG_SECS
txbuf[4] = RS5C348_CMD_MR(RS5C348_REG_SECS); /* cmd, sec, ... */
tm->tm_sec = bcd2bin(rxbuf[RS5C348_REG_SECS] & RS5C348_SECS_MASK);
ret = spi_w8r8(spi, RS5C348_CMD_R(RS5C348_REG_SECS));
txbuf[4] = RS5C348_CMD_MW(RS5C348_REG_SECS); /* cmd, sec, ... */
txp[RS5C348_REG_SECS] = bin2bcd(tm->tm_sec);