SDA5252 SIEMENS [Siemens Semiconductor Group], SDA5252 Datasheet - Page 55

• Manufacturer Part Number: SDA5252
• Description: TVTEXT 8-Bit Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

6.3.2.2
The internal data memory is divided into four blocks: the lower 128 byte of RAM, the
upper 128 byte of RAM, the 128-byte Special Function Register (SFR) area and the up
to 10 Kbyte additional RAM (Figure 21). Because the upper RAM-area and the SFR-
area share the same address locations, they are accessed through different addressing
modes.
The internal data RAM-address space is 0 to 255. Four banks of eight registers each
occupy locations 0 through 31. Only one of these banks may be enabled at a time
through a two-bit field in the PSW. In addition, 128-bit locations of the on-chip RAM are
accessible through direct addressing.
These bits reside in internal data RAM at byte locations 32 through 47, as shown in
Table 11. The lower 128 bytes of internal data RAM can be accessed through direct or
register-indirect addressing, the upper 128 bytes of internal data RAM through register-
indirect addressing and the special function registers through direct addressing.The
stack can be located anywhere in the internal data RAM-address space. The stack depth
is limited only by the available internal data RAM, thanks to an 8-bit relocatable stack
pointer. The stack is used for storing the program counter during subroutine calls and
may also be used for passing parameters. Any byte of internal data RAM or special
function registers accessible through direct addressing can be pushed/popped.
An additional on-chip RAM-space called “XRAM” extends the internal RAM-capacity.
The up to 10 Kbytes of XRAM are accessed by MOVX @DPTR. XRAM is located in the
upper area of the address space. 1 Kbyte of the XRAM, called VBI Buffer, is reserved
for storing teletext data and another up to 8 Kbyte of the XRAM, called Display Chapters,
are reserved for storing up to 8 display chapters (see Figure 21). Unused memory area
of the VBI Buffer and the Display Chapters can be used by the controller as general RAM
space.
:
Table 10
XRAM Address Space
Function
VBI Buffer
Display Chapter 0 - 7
CPU XRAM
(1)
(2)
Semiconductor Group
SDA 5251, SDA 5252 C000 - C3FF only
SDA 5250, SDA 5254 and SDA 5255 only
Internal Data RAM
Byte Address (hex.)
F400 - F7FF
C000 - DFFF
F800 - FBFF
55
(2)
(1)
SDA 525x
1998-04-08