tsc251g1dxxx-l12ced ATMEL Corporation, tsc251g1dxxx-l12ced Datasheet - Page 12

• Manufacturer Part Number: tsc251g1dxxx-l12ced
• Description: 8/16-bit Microcontroller With Serial Communication Interfaces - 32kbytes Rom
• Manufacturer: ATMEL Corporation

Data Memory
12
AT/TSC8x251G2D
The TSC80251G2D derivatives implement 1 Kbyte of on-chip data RAM. Figure 5
shows the split of the internal and external data memory spaces. This memory is
mapped in the data space just over the 32 bytes of registers area (see TSC80251 Pro-
grammers’ Guide). Hence, the part of the on-chip RAM located from 20h to FFh is bit
addressable. This on-chip RAM is not accessible through the program/code memory
space.
F o r f a s t e r c o m p u t a t i o n w i t h t h e o n - c h i p R O M / E P R O M c o d e o f t h e
TSC83251G2D/TSC87251G2D, its upper 16 KB are also mapped in the upper part of
the region 00: if the On-Chip Code Memory Map configuration bit is cleared (EMAP# bit
in UCONFIG1 byte, see Figure ). However, if EA# is tied to a low level, the
TSC80251G2D derivative is running as a ROMless product and the code is actually
fetched in the corresponding external memory (i.e. the upper 16 KB of the lower 32 KB
of the segment FF:). If EMAP# bit is set, the on-chip ROM is not accessible through the
region 00:.
All the accesses to the portion of the data space with no on-chip memory mapped onto
are redirected to the external memory.
Figure 5. Data Memory Mapping
ª47 KB
32 KB
32 KB
64 KB
64 KB
16 KB
compatibility with the C51 Architecture). When PC increments beyond the end of seg-
ment FE:, it continues at the reset address FF:0000h (linearity). When PC increments
beyond the end of segment 01:, it loops to the beginning of segment 00: (this prevents
from its going into the reserved area).
Memory Space
Data External
EMAP# = 1
EA# = 0
Data Segments
FD:FFFFh
FF:FFFFh
FF:7FFFh
FE:FFFFh
00:BFFFh
FF:8000h
FF:0000h
FE:0000h
Reserved
01:FFFFh
00:FFFFh
00:C000h
02:0000h
01:0000h
00:0420h
EA# = 1
EMAP# = 0
On-chip ROM/EPROM
Code Memory
32 bytes reg.
16 KB
16 KB
RAM Data
1 Kbyte
4135F–8051–11/06