ST10F276 datasheet(167/229 Pages) STMICROELECTRONICS

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ST10F276

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22.10

System configuration registers

The ST10F276 has registers used for a different configuration of the overall system. These

registers are described below.

Note:

SYSCON Reset Value is: 0000 0xx0 0x00 0000b

SYSCON (FF12h / 89h)

SFR

Reset value: 0xx0h

987

6543210

STKSZ

ROM

SGT

DIS

ROM

BYT

DIS

CLK

CFG

PWD

CFG

OWD

DIS

BDR

STEN

XPEN

VISI

BLE

XPER-

Table 77.

SYSCON description

Bit

Function

XPER-SHARE

XBUS peripheral share mode control

‘0’: External accesses to XBUS peripherals are disabled.

‘1’: XRAM1 and XRAM2 are accessible via the external bus during hold mode.

External accesses to the other XBUS peripherals are not guaranteed in terms of

AC timings.

VISIBLE

Visible mode control

‘0’: Accesses to XBUS peripherals are done internally.

‘1’: XBUS peripheral accesses are made visible on the external pins.

XPEN

XBUS peripheral enable bit

‘0’: Accesses to the on-chip X-peripherals and XRAM are disabled.

‘1’: The on-chip X-peripherals are enabled.

BDRSTEN

Bidirectional reset enable

‘0’: RSTIN pin is an input pin only. SW Reset or WDT Reset have no effect on this

pin.

‘1’: RSTIN pin is a bidirectional pin. This pin is pulled low during internal reset

sequence.

OWDDIS

Oscillator watchdog disable control

‘0’: Oscillator Watchdog (OWD) is enabled. If PLL is bypassed, the OWD monitors

XTAL1 activity. If there is no activity on XTAL1 for at least 1

µs, the CPU clock is

switched automatically to PLL’s base frequency (from 750 kHz to 3 MHz).

‘1’: OWD is disabled. If the PLL is bypassed, the CPU clock is always driven by

XTAL1 signal. The PLL is turned off to reduce power supply current.

PWDCFG

Power down mode configuration control

‘0’: Power Down Mode can only be entered during PWRDN instruction execution if

NMI pin is low, otherwise the instruction has no effect. To exit Power Down Mode,

an external reset must occur by asserting the RSTIN pin.

‘1’: Power Down Mode can only be entered during PWRDN instruction execution if

all enabled fast external interrupt EXxIN pins are in their inactive level. Exiting this

mode can be done by asserting one enabled EXxIN pin or with external reset.

CSCFG

Chip select configuration control

‘0’: Latched Chip Select lines, CSx changes 1 TCL after rising edge of ALE.

‘1’: Unlatched Chip Select lines, CSx changes with rising edge of ALE.

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