SAB80C515A-5 SIEMENS [Siemens Semiconductor Group], SAB80C515A-5 Datasheet - Page 19

• Manufacturer Part Number: SAB80C515A-5
• Description: 8-Bit CMOS Single-Chip Microcontroller Family
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

Figure 3-4
Use of Port 2 as I/O-Port
At a write to Port 2, XRAM address in XPAGE-register will be overwritten because of the concurrent
write to Port 2 and XPAGE-register. So whenever XRAM is used and the XRAM address differs
from the byte written to Port 2 latch it is absolutely necessary to rewrite XPAGE with page address.
Example:
I/O-Data at Port 2 shall be 0AA H . A Byte shall be fetched from XRAM at address 0F830 H
MOV R0, #30 H
MOV P2, #0AA H
MOV XPAGE, #0F8 H
MOVX A, @R0
Semiconductor Group
; P2 shows 0AA H
; P2 still shows 0AA H but XRAM is addressed
; the contents of XRAM at 0F830 H is moved to accu
3-12
Memory Organization