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Chapter 6: Using the Emulator
Using the EMSIM Registers
Using the EMSIM Registers
The 68360 processor contains a System Integration Module (SIM) which has the
external bus interface, eight chip selects, and other circuitry to reduce external
logic in a typical microprocessor system. The SIM can be programmed or
configured in a variety of ways to suit the need of various systems.
The HP 64780 emulator contains circuitry that accommodates the flexibility of the
SIM and maintains consistent emulation features.
The 68360 SIM is configured through the registers in the SIM register class; these
registers control how the 68360 uses external signal lines to access memory.
The emulator is configured through the registers in the EMSIM register class. This
programming controls how the emulator interprets the signals from the 68360 when
accessing emulation memory and passing information to the analysis trace.
Normally, the SIM and EMSIM registers should be programmed with the same
values so they will be working together.
One of the primary functions is to provide A31-A28 to the memory mapper and
analyzer so they will have the complete 32-bit address bus. This is easy if Port E of
the 68360 is programmed as address lines; however, if these lines are programmed
as write enables, the corresponding address lines are not available external to the
68360. The chip selects, however, have access to the full 32-bit address inside the
68360. You can therefore locate memory using a chip select at an address that is
not possible to decode externally. The emulator can use information in the
programming of the chip selects to re-create the upper address lines. This provides
a correct address in the analysis trace so that symbolic debugging is possible.
Unfortunately, these addresses cannot be recreated in time for memory mapping so
the mapper is limited to 28 bits of addressing when the upper address lines are not
available.
Normally, the emulator is programmed through the EMSIM registers to match the
programming of the 68360 SIM as it will exist after all of the boot-up configuration
is complete. This can be done before the boot-up code is run. In fact, the
programming of the EMSIM registers is part of the configuration and will be
loaded along with the memory map and other configuration items when a
configuration file is loaded.
The default programming of the EMSIM register set matches the reset values of the
68360 SIM (refer to the Motorola MC68360 User's Manual for specific values).
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