75
redigeringar
Bigi LED display: Skillnad mellan sidversioner
m
Fixed typo
Didrik (diskussion | bidrag) (Skapade sidan med 'miniatyr|The Bigi display with lights off miniatyr|The Bigi display with lights on ==Description...') |
Didrik (diskussion | bidrag) m (Fixed typo) |
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| Rad 41: | Rad 41: | ||
# '''Idle:''' Clk is low. Data 1/2 are "don't care". During this period the display is off. | # '''Idle:''' Clk is low. Data 1/2 are "don't care". During this period the display is off. | ||
# '''Data transfer:''' 2 packets of 64 bits are transferred on each of the data lines, to the shift registers. Each new bit is shifted in | # '''Data transfer:''' 2 packets of 64 bits are transferred on each of the data lines, to the shift registers. Each new bit is shifted in from the data lines on the rising edge of clk. The display is kept off during this period by the control circuitry on the panel boards. If it wasn't, a lot of random image data would be shown on the display as it's shifted out to its final destination. The meaning of the bits is described below. The stock controller has a 200 ns low/300 ns high timing for clk, but this should be pretty lax as long as you don't leave clk high for long enough to strobe the LEDs, or run it too fast for the 74LS logic on the board. | ||
# '''Strobe:''' After the last pulse data transfer is performed, clk is left at high signal level, which enables display output after a few microseconds. This lights up one line segment of the display with the data that was just transmitted. The length of the strobe time is controlled by the external device, but the stock controller is using a 720 µs strobe time. | # '''Strobe:''' After the last pulse data transfer is performed, clk is left at high signal level, which enables display output after a few microseconds. This lights up one line segment of the display with the data that was just transmitted. The length of the strobe time is controlled by the external device, but the stock controller is using a 720 µs strobe time. | ||
# '''Idle:''' After the strobe, clk is pulled low which blanks the display. The stock controller leaves it low for 6.5 µs but it was measured that the line segment was typically turned off after 2 µs. Because 74x164 is clocked on rising edges but not falling edges, this does not produce a glitch during this period. This is also the next idle period, (1). | # '''Idle:''' After the strobe, clk is pulled low which blanks the display. The stock controller leaves it low for 6.5 µs but it was measured that the line segment was typically turned off after 2 µs. Because 74x164 is clocked on rising edges but not falling edges, this does not produce a glitch during this period. This is also the next idle period, (1). | ||