IP2022 User’s Manual—System Architecture www.ubicom.com 17 The IP2022 has a mechanism for in-system programming of its
flash   and   RAM   program   memories   through   a   four-wire   SPI
interface. This provides easy programming and reprogramming of
devices   on   assembled   circuit   boards.   In   addition,   the   flash
memory can be programmed by software at run time, for example
to store user-specific data such as phone numbers and to receive
software upgrades downloaded over the Internet. The IP2022 also
has   an   on-chip   debugging   facility   which   makes   the   internal
operation of the chip visible to third-party debugging tools. 2.1 CPU Registers Figure 2-1 shows the CPU registers, which consist of seven 8-bit
registers, seven 16-bit registers, and one 24-bit register. The 16-
bit registers are formed from pairs of 8-bit registers, and the 24-bit
register is formed from three 8-bit registers. See Appendix C for a
complete list of CPU and peripheral registers.