Step 2. Set Up Your Chip-Selects - HP 64746 User Manual

Chapter 5: Plugging into a Target System
Configuring the Emulator for In-Circuit Operation

Step 2. Set up your chip-selects

The 68302 has 4 chip-selects, only one of which is enabled after a reset condition.
Nearly all 68302 target systems rely on at least one chip-select for accesses to
memory. If you are going to access any target memory that relies on a chip-select,
then you MUST be sure that the appropriate chip-select registers are initialized
first. In some cases, even executing code from emulation memory will require that
you first initialize your chip selects. This can be done in one of two ways:
Method 1: Using a Command File to Setup Chip-Selects:
Use a series of commands or a command file that modifies the registers to the
values you will need. For example, here is a command file that sets up CS0 and
CS1.
reset <RETURN>
break <RETURN>
modify register r302 bar to 800H <RETURN>
modify register chip_sel or0 to 3FC2H <RETURN>
modify register chip_sel br0 to 0001H <RETURN>
modify register chip_sel or1 to 1F80H <RETURN>
modify register chip_sel br1 to 0801H <RETURN>
Note It is important that you first modify the BAR register BEFORE you attempt to
modify the chip-select registers because the location of those registers is calculated
based on the value in the BAR.
The above example will map the Internal system registers to location 800XXXH,
and then initialize CS0 as a read-only, 1 wait-state block from 0 through 01FFFFH
and CS1 as a read-write, 0 wait-state block from 400000H through 43FFFFH.
If you are going to load your initialization code into target RAM using the
emulator, then you must use Method 1.
Method 2: Using Your Initialization Code to Setup Chip-Selects:
Execute a small section of your initialization code that sets up the proper values in
the chip select registers, and break into the monitor immediately after that, using
either a software or analysis breakpoint.
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