Address Decoder (DEC)
497
SNIU028A – February 2016 – Revised April 2016
Copyright © 2016, Texas Instruments Incorporated
Control System Module
16.1 Address Decoder (DEC)
The Address Decoder generates the memory selects for Flash, ROM and RAM arrays. The memory map
addresses are selectable through configurable register settings for low and high boundaries. These fine
memory selects can be configured from 1K to 16M sizes. Power on reset uses the default addresses in
the memory map for ROM execution, which is then configured by the ROM code to the application setup.
During access to the DEC registers, a wait state is asserted to the CPU. DEC registers are only writable in
the Privilege mode for user mode protection.
The DEC Address Manager controls memory mapping and flash programming. All memory mapping
activity is normally done by the boot ROM. This is described in this document. This information is only
useful if there is some need to return to ROM mode without going through a reset first.
There may be a need for customer programs to erase and program both Program and Data Flash, so this
is discussed in some detail.
16.1.1 Memory Mapping Basics
There are 4 memory address spaces in the UCD3138. Each memory space has a pair of registers to set
its address and block size:
Register
Number
Memory
Size in Bytes
Address at
Reset
Address in ROM Mode
Address in Flash Mode
0
Boot ROM
4K
Most of space
0x0000 0000 -
0x0000 FFFF
0x0000 A000 -
0x0000 AFFF
1
Program Flash
32K
-
0x0001 0000 -
0x0001 7FFFF
0x0000 0000 -
0x0000 7FFFF
2
Data Flash
2K
-
0x0001 8800 - 0x0001 8FFF
3
RAM
4K
-
0x0001 9000 - 0x0001 9FFF