Texas Instruments C28 Series Student Guide

Direct Addressing
Direct Addressing
Direct addressing allows for access to the full 4-Meg words space in 64 word “page” groups. As
such, a 16-bit Data Page register is used to extend the 6-bit local address in the instruction word.
Programmers should note that poor DP management is a key source of programming errors.
Paged direct addressing is fast and reliable if the above considerations are followed. The watch
operation, recommended for use whenever debugging, extracts the data page and displays it as the
base address currently in use for direct addressing.
Direct Addressing
Direct Addressing
–
–
“@”
“@”


Data memory space divided into 65,536 pages with
Data memory space divided into 65,536 pages with
64 words on each page
64 words on each page
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
Data page pointer (DP) used to select active page
Data page pointer (DP) used to select active page


16
16
-
-
bit DP is concatenated with a 6
bit DP is concatenated with a 6
-
-
bit offset from the
bit offset from the
instruction to generate an absolute 22
instruction to generate an absolute 22
-
-
bit address
bit address


Access data on a given page in any order
Access data on a given page in any order
00 0000 0000 0000 00 00 0000
00 0000 0000 0000 00 00 0000
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•
•
•
•
•
Page 0: 00 0000
Page 0: 00 0000
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–
00 003F
00 003F
00 0000 0000 0000 00 11 1111
00 0000 0000 0000 00 11 1111
00 0000 0000 0000 01 00 0000
00 0000 0000 0000 01 00 0000
•
•
•
•
•
•
Page 1: 00 0040
Page 1: 00 0040
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–
00 007F
00 007F
00 0000 0000 0000 01 11 1111
00 0000 0000 0000 01 11 1111
00 0000 0000 0000 10 00 0000
00 0000 0000 0000 10 00 0000
•
•
•
•
•
•
Page 2: 00 0080
Page 2: 00 0080
–
–
00 00BF
00 00BF
00 0000 0000 0000 10 11 1111
00 0000 0000 0000 10 11 1111
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
11 1111 1111 1111 11 00 0000
11 1111 1111 1111 11 00 0000
•
•
•
•
•
•
Page 65,535: 3F FFC0
Page 65,535: 3F FFC0
–
–
3F FFFF
3F FFFF
11 1111 1111 1111 11 11 1111
11 1111 1111 1111 11 11 1111
Offset
Offset
Data Page
Data Page
Data Memory
Data Memory
B - 8 C28x - Appendix B - Addressing Modes

Texas Instruments C28 Series Specifications

General

Brand	Texas Instruments
Model	C28 Series
Category	Computer Hardware
Language	English