Siemens EF 88H Series Manual de usuario descargar pdf (Pagina 42)

Semiconductor Group 6-8

On-Chip Peripheral Components

C501

6.1.2 Alternate Functions

The pins of ports 1 and 3 are multifunctional. They are port pins and also serve to implement special

features as listed in table 6-4.

Figure 6-9 shows a functional diagram of a port latch with alternate function. To pass the alternate

function to the output pin and vice versa, however, the gate between the latch and driver circuit must

be open. Thus, to use the alternate input or output functions, the corresponding bit latch in the port

SFR has to contain a one (1); otherwise the pulldown FET is on and the port pin is stuck at 0. After

reset all port latches contain ones (1).

Figure 6-9

Circuitry of Ports 1 and 3

MCS01827

CLK

Bit

Latch

Internal

Pull Up

Arrangement

Read

Latch

Read

Write

Int. Bus

Alternate

Output

Function

Alternate

Input

Function

1 2 ... 37 38 39 40 41 42 43 44 45 46 47 ... 120 121

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Siemens EF 88H Series Manual de usuario Pagina 42