[SOLVED] pull-up or pull-down resistor on LOAD of MAX7219

Other Hardware LEDs and Multiplexing
1

Some people refer to the pin as Chip Select, but according to the MAX7219, ~CS is for the MAX7221.
On the MAX7219 it is suppose to be LOAD.

Anyway, Nick Gammon on his forum mentions using a 10K pull-down on LOAD.

yet, Paul__B says he uses a 47K pull-up to VCC for LOAD.
max7219 code problem - LEDs and Multiplexing - Arduino Forum (reply #5) and 8x8 LED Matrix with MAX7219 - troubleshooting (how to connect HL-M1388BR) - LEDs and Multiplexing - Arduino Forum (reply #5)

Why the discrepancy?

2

I have used many MAX7219s in designs, with SPI.transfer() for sending it data.
The LOAD pin acts as an active low chip select.

digitalWrite (csPin, LOW);
SPI.transfer(registerAddress);
SPI.transfer(dataByte);
digitalWrite (csPin, HIGH);

MAX7219: "Load-Data Input. The last 16 bits of serial data are latched on LOAD’s rising edge."
MAX7221: "Chip-Select Input. Serial data is loaded into the shift register while CS is low. The last 16 bits of serial data are latched on CS’s rising edge."

So for the MAX7219, you could do the 2 SPI transfers and then toggle LOAD from Low-High-Low.
while for MAX7221 you need to drive it from High to Low, do the transfers, then bring it back high.
The MAX7219 also works properly with the same sitting at high, bring low for the transfers, then bring it back high.

3

A pullup or pulldown, either one will keep the line from bouncing around during an Arduino power up, or reset, or bootloading, or loading code via ICSP.

4

Thank you for the thorough explanation.
I wanted to make sure I had all the proper connections.

I cannot wait to finish my 1x4 using 8x8 LED matrix and MAX7219.

5

ieee488:
Anyway, Nick Gammon on his forum mentions using a 10K pull-down on LOAD.
Gammon Forum : Electronics : Microprocessors : Interfacing LED displays with the MAX7219 driver

yet, Paul__B says he uses a 47K pull-up to VCC for LOAD.
max7219 code problem - LEDs and Multiplexing - Arduino Forum (reply #5) and 8x8 LED Matrix with MAX7219 - troubleshooting (how to connect HL-M1388BR) - LEDs and Multiplexing - Arduino Forum (reply #5)

Why the discrepancy?

Well, my take is that it is active LOW, so if you do not want it to be spuriously activated, you pull it HIGH until the Arduino takes control.

I wonder what Nick thinks?