Using the External Memory Interface for I/O expansion

AN2591

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4.2

In this section, the same hardware structure is implemented as described in Section 4.1,

except that a 16-bit latch (74LCX16373) and 16-bit buffer (74LCX16244) are used.

It is important to know the propagation delay times of the devices you are using in order to

configure the corresponding number of wait states (Refer to the 74LCX16373,

74LCX16244, 74V1G02 and 74V1G08 datasheets).

Figure 12.

16-channel expander

74LCX16373

WRL

16 outputs

D[0..15]

CSn.x

RD

74LCX16244

2OE

1A-2A-3A-4A

16

D[0..15]

2LE

D[0..15]

1G

2G

EMI

data bus

1Y-2Y-3Y-4Y

1D-2D[0..16]

1Q-2Q[0..16]

16 inputs

16

1LE

1OE

3G

4G

74V1G02

74V1G08

1

48

25

24

1

48

25

24

16

16

16

16

3.3v

VDD*

GND*

3.3v

VDD*

GND*

Note (*): The VDD and GND power inputs of 74LCX16373 and 74LCX16244 are not all

represented in this figure: VDD pins of the two devices are: 7, 18, 31 and 42, must connected to

All GND pins of the two devices are: 4, 10, 15, 21, 28, 34, 39 and 45, must connected to ground.

For more details refer to the IC datasheets.

3.3V.

STR710