features for providing a glueless interface to an external MC68EC040 (or other M68040 family member), called MC68040 companion mode. The following Design Concept outlines a method whereby a MC68EC040/360 system may be booted from a single 8-bit Eprom. It is assumed that the reader is familiar with both the MC68EC040 and the Freescale Semiconductor, Inc... MC68360 nomenclature. SYSRESET CLK MC68EC040 MC68360 26V12 BR BR040 BR BR RESET RESET040 RESET360 R ESET CFG2 C FG2 EPROM_CS PORTX PORTX SRAM_CS C S0 C S0 C S1 C S1 5-BIT COUNTER EPROM_CS SRAM_CS Figure 1. Block Diagram for 360/040 8-Bit Boot Eprom System Overview In many embedded designs it is desirable to have an 8-bit boot Eprom to hold the application code. This saves on both cost and board space. Unfortunately the MC68EC040 does not directly support dynamic bus sizing, and without external hardware requires code to be held in 32-bit wide memory. There are several solutions to this problem, including using an external dynamic bus sizer, such as the MC681