Panasonic MN103001G/F01K - Manual (Page 188)

Bus Controller (BC)
8-74
2.
_____
Designate the bus authority request pin (BR) as a general-purpose input port, and the bus authority release
_____
pin (BG) as a general-purpose output port, for instance, so that bus requests cannot be accepted during
execution of a BSET or BCLR instruction.