Holt Integrated Circuits
12
2.
Press key ‘m’, a screen similar to the one below should be seen.
The sense data for Device1 on board1 and Device2 on board2 are displayed, a ‘1’ meaning a
high. Key ‘s’ can be used to just do one read. LED[1:8] also monitor the eight input states.
External SPI Operation
The HI-8400 devices are normally controlled through the on-board MCU. If required, an external
SPI master connected to J7 can be used. When using this method close jumper J1 to hold the
MCU RESET pin low, this forces the MCU GPIOs into a high impedance state. For normal
operation, keep this jumper open and use the RESET button to reset the MCU during testing.
Power should be connected between the VDD terminal and ground. The SPI controller should
then be connected to J7, using the following pin connections:
SPI Connector (J7)
Pin
Number
Label
Description
1
VLOGIC
3.3V or 5V Logic supply
2
nCS
SPI Chip Select
3
SCK
SPI Serial Clock Input
4
SI
SPI Serial Data Input
5
SO
SPI Serial Output from U3
6
INTB
Interrupt output from U3
7
GND
Low voltage Ground
