B.1.5 Memory Protection

The ability to inhibit writes to physical memory was added. The sixteen 64 KB physical memory blocks can be individually protected, and two of those blocks can additionally be subdivided and protected at a granularity of 4 KB. When a write is attempted, a new Priority 3 write-protection interrupt request is generated.

The write-protection can be enabled for the User mode only or for all modes (see Appendix C for more information).

WPHR = 0x85

WPLR = 0x6C

0xFFFFF

0x00000

WPSAR = 0x04

WPSAHR = 0x07

WPSALR = 0xCC

0x4FFFF

0x48000

0x40000

Figure B-1. Sample Memory Protection Layout

The new memory-protection registers are listed in Table B-6through Table B-11.

Table B-6. Write Protect Control Register

Write Protect Control Register

(WPCR)

(Address = 0x0440)

 

 

 

 

 

Bit(s)

Value

 

Description

 

 

 

 

7:1

 

These bits are reserved and should be written with zeros.

 

 

 

 

0

0

write-protection in User mode only.

 

 

 

 

 

1

write-protection in System and User modes.

 

 

 

 

 

 

 

 

284

Rabbit 3000 Microprocessor

Page 293
Image 293
Jameco Electronics 2000, 3000 manual Memory Protection, Table B-6. Write Protect Control Register, Wpcr