SC51D01Fxx

S51 MCU

SC51D01Fxx series use S51 MCU compatible with MCS-51 instructions. Users can develop the software using

standard 805x assembler and compiler.

The difference between S51 MCU and standard 8051 lies in:

S51 MCU supports dual DPTR.

In the condition of the same external oscillator frequency, the instruction period of S51 MCU is

shorter than that of 8051.

S51 MCU supports two extended RAM.

S51 MCU’s MOVX A,@Ri and MOVX @Ri, A commands can only access 00H~FFH of on-chip

XRAM.

S51 MCU only supports 2 interrupt sources: the overflow interrupt of timer 0 and timer 1. The

interrupt vector is different from that of standard 8051.

S51 MCU only supports 2 working modes: normal working and standby modes. The working mode

control is also different from that of standard 8051.

RESET

SC51D01Fxx series has external reset, keying reset, power down reset and watchdog reset 4 reset sources.

Where, the external reset, keying reset and power down reset can make the chip awake from standby mode.

External rset

External reset is adding a no less than 10ms low level on pin nRST to make MCU reset.

Connect tandem resistor and capacitor to pin nRST to implement the power on reset of MCU, shown in Fig. 4:

Fig. 4– External reset and power on reset circuit

Keying reset

Keying reset means that when MCU is in standby mode, apply effective time of low level to any one or more

keyboard input ports among KI0~KI7 to make MCU reset. This is often used to awake the MCU by keying.

In normal working mode, applying low level to KI0~KI7 will not make the MCU reset.

Power down reset

state, and enter normal working state.

Watchdog reset

The watchdog reset make MCU reset when the internal 20-bit counter (watchdog timer WDT) overflows. The

HANGZHOU MICROELECTRONICS CO.,LTD

REV:1.0

2007.12.03

Page 9 of 21