MSB
- clear the MSB of TX control register; &= ~0x80,
val.subword[MSB] = 123; \
ATF_CHECK_EQ_MSG(val.subword[MSB], 123, \
"val.subword[MSB] = 0x%" SUBFMT, val.subword[MSB]); \
val.subword[MSB] = 45; \
ATF_CHECK_EQ_MSG(val.subword[MSB], 45, \
"val.subword[MSB] = 0x%" SUBFMT, val.subword[MSB]); \
val.subword[MSB] = 123; \
ATF_CHECK_EQ_MSG(val.subword[MSB], 123, \
"val.subword[MSB] = 0x%" SUBFMT, val.subword[MSB]); \
val.subword[MSB] = 45; \
ATF_CHECK_EQ_MSG(val.subword[MSB], 45, \
"val.subword[MSB] = 0x%" SUBFMT, val.subword[MSB]); \