ST10R272L - CENTRAL PROCESSING UNIT
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Note
SYSCON register cannot be changed after execution of the EINIT instruction.
The function of bits XPER-SHARE, VISIBLE, WRCFG, BYTDIS, ROMEN and
ROMS1 is described in more detail in “EXTERNAL BUS INTERFACE” on
page 145.
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 selects 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 therefore, 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
ROMEN
Internal ROM Enable (Set according to pin EA during reset)
‘0’: Internal ROM disabled: accesses to the ROM area use the external bus
‘1’: Internal ROM enabled
This bit is not relevant on the ST10R262 since it does not include internal ROM. It
should be kept to 0
SGTDIS
Segmentation Disable/Enable Control
‘0’: Segmentation enabled (CSP is saved/restored during interrupt entry/exit)
‘1’: Segmentation disabled (Only IP is saved/restored)
ROMS1
Internal ROM Mapping
‘0’: Internal ROM area mapped to segment 0 (00’0000h...00’7FFFh)
‘1’: Internal ROM area mapped to segment 1 (01’0000h...01’7FFFh)
This bit is not relevant on the ST10R262 since it does not include internal ROM. It
should be kept to 0.
STKSZ
System Stack Size
Selects the size of the system stack (in the internal RAM) from 32 to 1024 words
Bit
Function
