SC65D02P40

[Function description]

When external reset occurs, the initial value of timer(WDT_TimerH, WDT_TimerL)and 21-bit watchdog counter

are both cleared.

When use the clear module to reset the watchdog timer, the high 5-bit of the watchdog counter is cleared, the

low 16-bit will be loaded from the initial value register of timer again and begin to count.

When the low 16-bit of watchdog counter counts to FFFFH, the timer will overflow if increasing by 1 , then

reload the initial value of timer; At this time, if the interrupt mask bit (WDT_MASK)=“0” and the timer interrupt

enable bit(WDT_TimerEn)=“1”, it will generate timer interrupt signal, and WDT_FLAG is set.

Add 1 to the counting value of high 5-bit of watchdog timer when bit15 of watchdog counter changes from 1 to

0; the watchdog will generate reset signal if bit20 of watchdog counter changes from 1 to 0.

3.2 I/O ports

[Description]

SC65D02P40 includes three groups of I/O ports: P0, P1 and P2. P0 and P2 are 8-bit parallel ports, while P1 is

4-bit parallel port.

Each I/O port of SC65D02P40 can be set independently as weak pull-up input or push-pull output status. The

high level output capacity of the port is much bigger than low level output capacity, so it can identify the dual-

key or multi-key pressing at the same time.

[Structure]

Figure 4 – P0 structure

Note: The structure of P1 and P2 is the same as P0.

[Function description]

As shown in figure 4, we take P0 for example to introduce the I/O port function. The function of P1 and P2 is

the same with that of P0.

When P0_Ctrl[n] is set, PMOS P1 and NMOS N1 are both off, PMOS P2 is on, pull-up resistor Rpu is active,

and port P0n is input mode.

When P0_Ctrl[n] is cleared, PMOS P2 is off, port P0n is output mode. At this time, when P0_Data[0] is set,

PMOS P1 is on, NMOS N1 is off, and port P0n outputs high level; when P0_Data[0] is cleared, PMOS P1 is

off, NMOS N1 is on, and port P0n outputs low level.

HANGZHOU SILAN MICROELECTRONICS CO.,LTD

REV:1.2

2008.07.21

Http: //www.silan.com.cn

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