p89lpc904 NXP Semiconductors, p89lpc904 Datasheet - Page 12

• Manufacturer Part Number: p89lpc904
• Description: 8-bit Microcontrollers With Two-clock Accelerated 80c51 Core 1 Kb 3 V Byte-erasable Flash With 8-bit A/d Converter
• Manufacturer: NXP Semiconductors

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All ports are in input only (high-impedance) state after power-up.
BRGR1 and BRGR0 must only be written if BRGEN in BRGCON SFR is logic 0. If any are written while BRGEN = 1, the result is unpredictable.
Unimplemented bits in SFRs (labeled ’-’) are X (unknown) at all times. Unless otherwise specified, ones should not be written to these bits since they may be used for other
purposes in future derivatives. The reset values shown for these bits are logic 0s although they are unknown when read.
The RSTSRC register reflects the cause of the P89LPC904 reset. Upon a power-up reset, all reset source flags are cleared except POF and BOF; the power-on reset value is
xx110000.
After reset, the value is 111001x1, i.e., PRE2-PRE0 are all logic 1, WDRUN = 1 and WDCLK = 1. WDTOF bit is logic 1 after Watchdog reset and is logic 0 after power-on reset.
Other resets will not affect WDTOF.
On power-on reset, the TRIM SFR is initialized with a factory preprogrammed value. Other resets will not cause initialization of the TRIM register.
The only reset source that affects these SFRs is power-on reset.
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