C505_9708 SIEMENS [Siemens Semiconductor Group], C505_9708 Datasheet - Page 44

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

4.4
The C505 allows to switch off the ALE output signal. If the internal ROM is used (EA=1 and PC
3FFF H ) and ALE is switched off by EALE=0, then, ALE will only go active during external data
memory accesses (MOVX instructions). If EA=0, the ALE generation is always enabled and the bit
EALE has no effect.
After a hardware reset the ALE generation is enabled.
Special Function Register SYSCON (Address B1 H )
Bit
EALE
–
Semiconductor Group
B1 H
ALE, Address Latch Enable
Bit No. MSB
7
–
The shaded bits are not described in this section.
Function
Enable ALE output
EALE = 0 :
EALE = 1 :
If EA=0, the ALE generation is always enabled and the bit EALE has no
effect on the ALE generation.
Reserved bits for future use. Read by CPU returns undefined values.
6
–
EALE RMAP CMOD
5
ALE generation is disabled; disables ALE signal generation
during internal code memory accesses (EA=1). With EA=1,
ALE is automatically generated at MOVX instructions.
ALE generation is enabled
4
4-4
3
2
–
XMAP1
1
External Bus Interface
Reset Value : XX100X01 B
XMAP0
LSB
0
C505 / C505C
SYSCON
1997-08-01