Abstract: A microprocessor or microcontroller architecture which utilizes a 64 byte-register file in a unique manner. The lowest 16 bytes of the register file can be accessed as 16 8-bit registers (R0-R15), the lowest 32 bytes can also be accessed as 16 32-bit (word) registers (WR0-WR30), and the entire register file can be accessed as 16 64-bit (double word or Dword) registers (DR0-DR60). In this manner, various combinations of 8/16/32-bit registers are provided without wasting the register file. While providing at least 16 8/16/32-bit registers, only four bits are necessary to encode a register, thereby allowing two byte register-to-register instructions. The register file and an instruction sequencer operate to provide the 64 byte-register file which can be accessed so that the lowest 16 bytes of the register file are accessed as 16 8-bit registers (R0-R15), the lowest 32 are accessed as 16 word registers (WR0-WR30), and the entire register file is accessed as 16 double word registers (DR0-DR60).

Abstract: A microcontroller or microprocessor architecture with a multiplexed address and data bus wherein the high order address bits are multiplexed with the low order data bits. Under this scheme, the low order address bits are connected directly to the memory and the high order address bits are latched by an address latch which captures the data on the bus when an address latch enable (ALE) signal is asserted. With the high order address bits multiplexed with the data bits, multiple data transfers can be performed without repeated address cycles since there is no need to place the high address bits which have already been latched on the multiplexed bus. The address and data buses are demultiplexed when the high order address bits are latched using ALE. When the address crosses the page boundary, the crossover is detected, by comparing the current high order address bits with the high order address bits of the previous bus cycle, and an address cycle is generated.