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C165UTAH
Central Processor Unit
Data Sheet
67
2001-02-23
Note:
Register SYSCON cannot be changed after execution of the EINIT instruction.
System Clock Output Enable (CLKEN)
The system clock output function is enabled by setting bit CLKEN in register SYSCON
to '1'. If enabled, port pin P3.15 takes on its alternate function as CLKOUT output pin.
The clock output is a 50 % duty cycle clock whose frequency equals the CPU operating
frequency (f
OUT
= f
CPU
).
Note:
The output driver of port pin P3.15 is switched on automatically, when the
CLKOUT function is enabled. The port direction bit is disregarded.
After reset, the clock output function is disabled (CLKEN = ‘0’).
Segmentation Disable/Enable Control (SGTDIS)
Bit SGTDIS allows to select either the segmented or non-segmented memory mode.
In non-segmented memory mode
(SGTDIS='1') it is assumed that the code address
space is restricted to 64 KBytes (segment 0) and thus 16 bits are sufficient to represent
all code addresses. For implicit stack operations (CALL or RET) the CSP register is
totally ignored and only the IP is saved to and restored from the stack.
In segmented memory mode
(SGTDIS='0') it is assumed that the whole address space
is available for instructions. For implicit stack operations (CALL or RET) the CSP register
and the IP are saved to and restored from the stack. After reset the segmented memory
mode is selected.
Note:
Bit SGTDIS controls if the CSP register is pushed onto the system stack in addition
to the IP register before an interrupt service routine is entered, and it is repopped
when the interrupt service routine is left again.
SGTDIS
Segmentation Disable/Enable Control
’
0
’
:
Segmentation enabled
(CSP and IP are saved/restored during interrupt entry/exit)
’
1
’
:
Segmentation disabled (Only IP is saved/restored)
Reserved
The ROMS1, known from other C16x Infineon derivatives, is
not
supported in
the C165UTAH. This bit must be set to
’
0
’
signal.
System Stack Size
Selects the size of the system stack (in the internal RAM) from 32 to 1024 words
ROMS1
STKSZ
Bit
Function