Echelon I/O Model Reference for Smart Transceivers and Neu Manuel d'utilisateur télécharger pdf (Page 51)

I/O Model Reference 41

The direction of nibble ports can be changed between input and output

dynamically under application control (see

Programming Considerations

on page

42). The least-significant bit (LSB) of the input data is determined by the object

declaration and can be any of the IO0 – IO4 pins.

For Series 3100 devices, the high (20 mA) current sink capability of pins IO0 –

IO3 (see

Figure 14) allows these pins to drive many I/O devices directly.

Figure 14. Nibble Input/Ouput

Figure 15 and Figure 16 on page 42 show the nibble input and nibble output

latency times, respectively. These are the times from the call to the io_in() or

io_out() function, until a value is returned. The direction of bit ports can be

changed between input and output dynamically by using the io_set_direction()

function.

Figure 15. Nibble Input Timing

Table 16. Nibble Input Latency Values for Series 3100 Devices

Symbol Description Typical at 10 MHz

fin

Function call to sample

IO0 – IO4

41 μs

ret

Return from function

IO0

IO1

IO2

IO3

IO4

18 μs

22.8 μs

27.5 μs

32.3 μs

36 μs

1 2 ... 46 47 48 49 50 51 52 53 54 55 56 ... 208 209

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Echelon I/O Model Reference for Smart Transceivers and Neu Manuel d'utilisateur Page 51