Internal data memory, Ds80c400 – Maxim Integrated High-Speed Microcontroller Users Guide: Network Microcontroller Supplement User Manual
Page 98
Internal Data Memory
DS80C400
The DS80C400 incorporates 9472 bytes of internal SRAM memory, in addition to the standard 256-byte scratchpad memory. This addi-
tional on-chip SRAM is logically divided into three memory blocks: a 1kB block usable as data memory and extended stack memory,
an 8kB block usable as data memory and Ethernet transmit/receive buffer memory, and a 256-byte block usable as data memory and
CAN controller memory. In order for the 1kB internal SRAM to be used as extended stack memory, the stack address mode (SA) bit
contained in the ACON register, must be set to 1. The logical address location for each block is determined by the settings of the IDM1,
IDM0 bits and the CMA bit, all contained in the MCON (C6h) register. Table 6-1 summarizes the six possible configurations for the three
internal SRAMs, while Figure 6-2 illustrates three data memory map possibilities.
Table 6-1. Internal Data Memory Address Locations
IDM1:0
CMA
1kB SRAM
(OPTIONAL STACK)
8kB SRAM
(ETHERNET BCU)
256–BYTE SRAM
(CAN)
00
0
00DC00h–00DFFFh
00E000h–00FFFFh
00DB00h–00DBFFh
00
1
00DC00h–00DFFFh
00E000h–00FFFFh
FFDB00h–FFDBFFh
01
0
002000h–0023FFh
000000h–001FFFh
00DB00h–00DBFFh
01
1
002000h–0023FFh
000000h–001FFFh
FFDB00h–FFDBFFh
10
0
FFDC00h–FFDFFFh
FFE000h–FFFFFFh
00DB00h–00DBFFh
10
1
FFDC00h–FFDFFFh
FFE000h–FFFFFFh
FFDB00h–FFDBFFh
High-Speed Microcontroller User’s
Guide: Network Microcontroller
Supplement
98
Figure 6-2. Example Data Memory Map Configurations (DS80C400)
IDM1:0 = 10b; CMA = 1
Addressable
External
Memory
000000h
FFFFFFh
FFDC00h
FFDBFFh
FFE000h
FFDFFFh
~
~
~
~
Internal
8kB SRAM
(Ethernet BCU)
Internal
1kB SRAM
(Optional Stack)
256-byte SRAM
(CAN)
FFDB00h
FFDAFFh
IDM1:0 = 00b; CMA = 0
(DEFAULT)
Addressable
External
Memory
Addressable
External
Memory
000000h
FFFFFFh
00DC00h
00DBFFh
00E000h
00DFFFh
~
~
~
~
Internal
8kB SRAM
(Ethernet BCU)
Internal
1kB SRAM
(Optional Stack)
256-byte SRAM
(CAN)
00DB00h
00DAFFh
010000h
00FFFFh
IDM1:0 = 01b; CMA = 0
Addressable
External
Memory
Addressable
External
Memory
000000h
FFFFFFh
002400h
0023FFh
00DB00h
00DAFFh
~
~
~
~
256-byte SRAM
(CAN)
002000h
001FFFh
00DC00h
00DBFFh
Internal
1kB SRAM
(Optional Stack)
Internal
8kB SRAM
(Ethernet BCU)
Maxim Integrated