w83l950d Winbond Electronics Corp America, w83l950d Datasheet - Page 25

• Manufacturer Part Number: w83l950d
• Description: Peripheral Personal Computer Keyboard Controller
• Manufacturer: Winbond Electronics Corp America

6.10 External SRAM
The Winbond Keyboard controller has a 2K bytes external SRAM and is read/write accessible. The
SRAM begins at address 0000h to 07FFh, is accessed via the MOVX instruction in generally. There is
no conflict or overlap among the 256bytes scratch pad RAM and the 2K bytes external SRAM as they
use different addressing modes and separate instructions. The addressing of external SRAM can up to
64K bytes long.
6.11 Scratched ULTRA ROM
The external SRAM can be accessed by either general external memory instruction, i.e. MOVX, or to
be a scratch ROM for special purpose which achieved by re-mapping this area to a part of logical
Program Memory, addressed on 0F800h to 0FFFFh (62K to 64K), unlike the industry standard 8052
derivatives. No control switch is needed here. In other words, using MOVX to transfer data to and jump
to it by an absolutely JUMP instruction to accomplish this operation. This feature can increase the
system throughput and is convenient to perform On-Chip internal flash task.
Map to 62K-64K
PROGRAM
SPACE
40K PROGRAM
MEMORY
FFFFh
F800h
9FFFh
0000h
PROGRAM SPACE
Figure 3:Memory Map
Fig.5.3 Memory Map
- 16 -
DATA SPACE
07FFh
0000h
2K DATA MEMORY
W83L950D