bt_hi
REGWRITE32(p, bt_hi, 0x0f & ((r)>>8)); \
REGWRITE32((p), bt_hi, 0); \
REGWRITE32(p, bt_hi, 0x0f & ((r)>>8)); \
REG(vdac, bt_hi) = ((regno) & 0x0f00) >> 8; \
REG(vdac, bt_hi) = DUPBYTE1(regno); \
REGWRITE32((p), bt_hi, 0xff & ((r)>>8)); \
REGWRITE32((p), bt_hi, 0); \