The Breakpoint/Debug controller allows the RST 28 instruction to be used as a software breakpoint. Normally the RST 28 instruction causes a call to a particular location in mem- ory, but the operation of this instruction is modified when the breakpoint/debug feature is enabled. The RST 28 instruction is treated as a NOP in the breakpoint/debug mode.

Table 8-7. Breakpoint/Debug Control Register (BDCR, adr = 0x01C )

Breakpoint/Debug Control Register

(BDCR)

(Address = 0x01C)

 

 

 

 

 

Bit(s)

Value

 

Description

 

 

 

 

 

 

7

0

Normal RST 28 operation.

 

 

 

 

 

 

 

 

1

RST 28 is NOP.

 

 

 

 

 

 

6:0

 

These bits are reserved and should not be used.

 

 

 

 

 

 

8.6 Allocation of Extended Code and Data

The Dynamic C compiler compiles code to root code space or to extended code space. Root code starts in low memory and compiles upward.

Allocation of extended code starts above the root code and data. Allocation normally con- tinues to the end of the flash memory.

Data variables are allocated to RAM working backwards in memory. Allocation normally starts at 52K in the 64K D space and continues. The 52K space must be shared with the root code and data, and is allocated upward from zero.

Dynamic C also supports extended data constants. These are mixed in with the extended code in flash.

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Jameco Electronics 3000 Allocation of Extended Code and Data, Breakpoint/Debug Control Register BDCR, adr = 0x01C, Bdcr