2

I've struggled over an article from FTDI about the Latency Timer. Setting a Custom Default Latency Timer Value

... although 1ms is not recommended as this is the same as the USB frame length.

I've setup in several project the latency to 1ms (I want low round robin delays). So is this not recommended? Would be 2ms the "correct" alternative?

powerpete
  • 2,663
  • 2
  • 23
  • 49

2 Answers2

1

I don't know, how old the web page "Setting a Custom Default Latency Timer Value" is. Application note AN232B-04 does not have a special note for 1 ms latency timer.

Note: Latency timer matters only for small amounts of data (see page 6 of the application note) including last fragment of large data.

From my experience: FT2232C/L/D work fine with 1 ms latency, but in case of MPSSE mode SEND IMMEDIATE command gives even faster data transmission.

For UART mode an EVENT CHARACTER (one can set the character to '\n' in text mode or packet delimiter in packet mode) also triggers transmission with no regards on latency timer.

ReAl
  • 1,231
  • 1
  • 8
  • 19
0

As you can read in the linked documentation 2ms should be correct.

The valid range for the latency timer is 1ms - 255ms

just
  • 1,900
  • 4
  • 25
  • 46