Peripherals—IP2022 User’s Manual 238 www.ubicom.com Figure 4-2  Port B Interrupt Logic 4.1.2 Reading and Writing the Ports The  port  registers  are  memory-mapped  into  the  data  memory
address space between 0x020 and 0x03A. In addition, Port B has
three extra registers located between 0x017 and 0x019 which are
used to support external interrupt inputs. When  two  successive  read-modify-write  instructions  read  and
write the same I/O port with a very high clock rate, the “write” part
of one instruction might not occur soon enough before the “read” RB7 INTED Register 515-031.eps RB6 RB1 RB0 INTF Register INTE Register Port B
Interrupt