STLED316S

Key-scan & display cycle

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Key-scan & display cycle

The display RAM stores the data transmitted from an external device to the STLED316S

through the serial interface. Refer to Section 9: Key-scanning and display timing on page 25

for a pictorial representation.

The grid and segment outputs are controlled by the display output module. The entire grid

will be turned off on channel 1/16 and 16/16 meaning that the first channel and last channel

are off. This is referred to as blanking time.

During the keyscan time (first cycle from timing generator), the entire grid is turned off and

only the segments are enabled one by one (seg0 to seg7). The segment on time is 64 µs.

During the LED discrete time (second cycle), the data present on the internal LED buffer is

checked. If the data is present, then the brightness setting of each LED in the brightness

control register is checked. Then each segment will be enabled or disabled based on the

register value. In this duration, the grids 1 to 6 are turned off. The grid corresponding to LED

digit is turned on. The LED on duty cycle is 14/16. If the LED/seg1 brightness is 12/16, it

means that the segment1 OFF time is 12/16 and on time is 2/16.

it is ON or OFF. If display is ON, then the dimming settings are checked from the

configuration register for the grid (it may be common dimming setting or individual dimming

setting for each digit). The minimum turn on time is 1/16 and maximum turn on time is 14/16.

The blanking time is valid before the turning on and turning off of the grid. The blanking

interval is 32 µs. This will continue until the maximum number of digits configured in the

register. Once the full cycle is complete, the keyscan cycle will start again.

If the display is not turned on, then the timing generation will immediately go to the key scan

mode.

Initial:

All the segments and grids are turned off.

During operation:

1.

Turn on segment (keyscan) one by one. On time duration is 64 µs.

2.

Check the data present in LED register. If data is present, turn on the respective LED

grid and segments.

3.

Check the display on. If display is turned on, then enable the grid one by one from grid

1 to grid 6 (maximum) and turn on segments.