C517A 查看數據表（PDF） - Siemens AG

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C517A

8-Bit CMOS Microcontroller

Siemens AG 

Introduction

C517A

Table 1-1

Pin Definitions and Functions (cont’d)

6\PERO

P4.0 - P4.7

3LQ 1XPEHU

304)3 3/&&

64 - 66,

68 - 72

1 - 3,

5-9

PE/SWD

67

4

*) I = Input

O = Output

,2 )XQFWLRQ

I/O Port 4

is an 8-bit quasi-bidirectional I/O port with

internal pull-up resistors. Port 4 pins that

have 1’s written to them are pulled high by

the internal pull-up resistors, and in that

state can be used as inputs. As inputs, port

4 pins being externally pulled low will source

current (I IL, in the DC characteristics)

because of the internal pull-up resistors.

Port 4 also serves as alternate compare

functions. The output latch corresponding to

a secondary function must be programmed

to a one (1) for that function to operate. The

secondary functions are assigned to the

pins of port 4 as follows :

P4.0 - P4.7 CM0 - CM7 Compare

channel 0 - 7

I

Power saving mode enable / Start

watchdog timer

A low level at this pin allows the software to

enter the power saving modes (idle mode,

slow down mode, and power down mode).

In case the low level is also seen during

reset, the watchdog timer function is off on

default.

Usage of the software controlled power

saving modes is blocked, when this pin is

held at high level. A high level during reset

performs an automatic start of the watchdog

timer immediately after reset.

When left unconnected this pin is pulled

high by a weak internal pull-up resistor.

During hardware power down the pullup

resisitor is switched off.

Semiconductor Group

1-12

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