Matrix Orbital GLK12232-25-WBL - Manual (Page 18)

4.3.1 Enter Flow Control Mode (254 58 [full][empty])
NOTE Flow control applies only to the RS-232 interface. It is not available for I 2 C.
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 micro-controller. When the buffer empties so that only
[empty] bytes remain the display will return an "almost empty" message (0xFF) to the micro-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 the buffer is
almost full even though it may have already thrown rejected data away. The buffer size for the display is 96
bytes.
When using this command in an application, selection of the value for the buffer almost full should be
considered very carefully. This is a critical aspect of using this command to it’s full potential. When using a
host system or PC which contains a FIFO, the user should set the value of 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 should be set to 16 or greater.
NOTE This mode must not be used during loading of fonts and bitmaps. It is highly
recommended for use with direct screen write and multiple pixel placements.
4.3.2 Exit Flow Control Mode (254 59)
This command turns off flow control. Bytes may overflow the buffer without warning.
5 Keypad Interface
This chapter describes the keypad interface and associated commands in detail.
5.1 General
The display keypad interface processes the keypad row / column matrix into a serial (RS-232 or I 2 C)
data byte stream. Aside from this processing, the keypad has no effect on the display. If it is necessary to
send keystrokes to the display, they must be routed through the micro-controller.
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