PWM_MISC_REG_AB
misc = HREAD4(sc, PWM_MISC_REG_AB);
HCLR4(sc, PWM_MISC_REG_AB, (idx == 0) ? PWM_A_EN : PWM_B_EN);
misc = HREAD4(sc, PWM_MISC_REG_AB);
HWRITE4(sc, PWM_MISC_REG_AB, misc);
HSET4(sc, PWM_MISC_REG_AB, (idx == 0) ? PWM_A_EN : PWM_B_EN);