C505_9708 SIEMENS [Siemens Semiconductor Group], C505_9708 Datasheet - Page 29

• Manufacturer Part Number: C505_9708
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

Figure 3-4
Use of Port 2 as I/O Port
At a write to port 2, the XRAM/CAN controller 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 the page address.
Example :
I/O data at port 2 shall be AA H . A byte shall be fetched from XRAM at address FF30 H .
MOV
MOV
MOV
MOVX
Semiconductor Group
R0, #30H
P2, #0AAH
XPAGE, #0FFH
A, @R0
to Port 2
I/O Data
Write
XPAGE
Port 0
Port 2
;
; P2 shows AAH and XPAGE contains AAH
; P2 still shows AAH but XRAM is addressed
; the contents of XRAM at FF30H is moved to accumulator
3-8
CAN-Controller
XRAM
Memory Organization
Address/Data
I/O Data
C505 / C505C
MCS02763
1997-08-01