MC68150
Freescale Semiconductor
using an external dynamic bus sizer, such as the MC68150
Application NoteNxp
Implementing an 8-bit EPROM for an MC68EC040/MC68360 System
Describes a method to boot an MC68EC040/MC68360 system from a single 8-bit EPROM using the MC68360's IDMA and a PAL-based state machine to reduce costs and board space.
Overview
This application note outlines a design concept for booting an MC68EC040 and MC68360 (QUICC) system from 8-bit memory, despite the MC68EC040's lack of native dynamic bus sizing. The solution utilizes a 26V12 PAL to manage a state machine that initially boots the MC68360 in CPU-enabled mode. The MC68360 then uses its internal IDMA to copy application code from a cost-effective 8-bit EPROM into 32-bit wide SRAM. Upon completion, the PAL triggers a secondary reset sequence, switching the MC68360 into companion mode and allowing the MC68EC040 to boot directly from the 32-bit SRAM. This method eliminates the need for expensive external bus sizers like the MC68150.
Use Cases
- Reducing component count and board space in embedded MC68040 designs
- Lowering system cost by using 8-bit boot memory instead of 32-bit memory
- Implementing a glueless interface between MC68360 and MC68EC040 processors
- Designing bootloaders for systems requiring high-speed SRAM execution from low-speed EPROM storage
Topics
MC68360
MC68EC040
QUICC
8-bit EPROM
26V12 PAL
IDMA
Companion Mode
Dynamic Bus Sizing
Boot Sequence
SRAM
Referenced Parts
MC68360
Freescale Semiconductor
The MC68360 has a mode whereby the internal CPU32+ core may by disabled
MC68EC040
Freescale Semiconductor
providing a glueless interface to an external MC68EC040 (or other M68040 family member)
| MC68150 | Freescale Semiconductor | using an external dynamic bus sizer, such as the MC68150 |
| MC68360 | Freescale Semiconductor | The MC68360 has a mode whereby the internal CPU32+ core may by disabled |
| MC68EC040 | Freescale Semiconductor | providing a glueless interface to an external MC68EC040 (or other M68040 family member) |