Concepts Of The Emram - HP MC68360 User Manual

Chapter 13: Concepts of the EMSIM and EMRAM

Concepts of the EMRAM

The 68360 processor has internal RAM modules. These internal RAM modules
can be used like any other system RAM; that is, their memory hardware can be
assigned to support any desired address range within the 68360 address space.
The address range that a particular internal RAM module will support, and the
qualifiers that might additionally be assigned to that address range are defined by
the values contained within registers in the Memory Controller of the processor.
The values of these registers are supplied to the emulator as part of the EMRAM
copy. The emulator uses this information to determine where memory accesses
should be routed, based on the current emulator memory map.
The emulator cannot emulate internal RAM modules when the internal RAM is
enabled. Internal RAM accesses will typically not be seen outside the processor,
and therefore emulation memory will be ignored. The only way to get the
processor to access emulation memory which has been mapped to the same address
range as internal RAM is to disable the internal RAM, by resetting the processor.
Note that internal RAM accesses may be seen externally by the analyzer using the
show cycles feature, discussed below.
By default, the internal RAM modules in 68360 processor are turned off. The
internal RAMs are enabled and positioned by loading the EMRAM registers. The
contents of the EMRAM registers are automatically copied to the RAM registers
each time the emulator enters the monitor from emulation reset.
Concepts of Show Cycles
Typically when the processor accesses internal resources (either the Module
Control Block, or internal RAM) the bus cycles are not available external to the
processor. These bus cycles can be made available by enabling a feature of the
68360 processor called show cycles. In order to capture a trace of activity
involving these internal resources, the 68360 processor's show cycles feature is
used to make activity available to the analyzer. Two control bits in the SIM_MCR
register must be set to enable the show cycles feature. Specifically, these control
bits are bits 8 and 9 of the Module Configuration Register. These two bits control
external bus arbitration in addition to show cycles. Refer to the Motorola 68360
User Manual for detailed information of how to program these bits.
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