Matrix Orbital GLK240128-25 Legacy - Manual (Page 20)

4.2 Turn Flow Control On
Syntax Hexadecimal 0xFE 0x3A [full] [empty]
Decimal 254 58 [full] [empty]
ASCII 254 “:” [full] [empty]
Parameters Parameter Length Description
full 1 Bytes remaining before issuing a
almost full message. (Full is 0)
empty 1 Bytes available before issuing a
almost empty message. (Empty is
128)
Description This command enables flow control. When the buffer fills so that only
[full] bytes are available, the display will return an “almost full”
message (0xFE) to the host controller. When the buffer empties so that
only [empty] bytes remain, the display will return an “almost empty”
message (0xFF) to the host controller.
The display will return the “almost full” message for every byte sent to
the display until the used buffer space once more drops below the [full]
level. Whether the user is in ‘flow control mode’ or not, the module will
ignore display or command bytes which would overrun the buffer.
While in ‘flow control mode’ the unit will return 0xFE when buffer is
almost full even though it may have already thrown rejected data away.
The buffer size for the display is 128 bytes.
When using this command in an application, selection of the value for
the buffer [full] should be considered very carefully. This is a critical
aspect to be able to use this feature to it’s full potential. When using a
host system or PC which contains a FIFO, the user should set the value
of [full] equal to or greater than the size of the FIFO. The reason for this
is that the FIFO may be full when the host system receives 0xFE. In the
case of 16550 UART the size at its maximum is 16, therefore the value
of [full] should be set to 16 or greater. It is suggested that the “almost
full” parameter be equal to the largest chunk of data the host will be
sending the display (should be less than 127).
NOTE This command is not available in I 2 C mode.
Remembered Yes
Default Off
4.3 Turn Flow Control Off
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