AS1112
Datasheet - Detailed Description
9 Detailed Description
Serial Interface
The AS1112 features a versatile 3-pin (CLK, SDI, and SDO) serial interface, which can be connected to microcon-
trollers or digital signal processors in various configurations.
The rising edge of the CLK signal shifts data from pin SDI to the internal register. After all data is clocked in, the serial
data is latched into the internal registers at the rising edge of the LD signal.
Note: All data is clocked in with the MSB first.
Multiple AS1112 devices can be cascaded by connecting the SDO pin of one device with pin SDI of the next device
(see Figure 15 on page 15). The SDO pin can also be connected to the microcontroller to receive status information
from the AS1112. The serial data format is 96-bit or 192-bit wide, depending on mode of the device (see LD on page 2).
Figure 7. Serial Data Input Timing Diagram
Dot Correction Mode
Data Input Cycle
Greyscale Mode
Data Input Cycle
Dot Correction Mode
Data Input Cycle
MODE
tH3
tSU3
tH3
LD
DCn-1
LSB
DCn-1
MSB-1
DCn
MSB
DCn
LSB
GSn
MSB
GSn
LSB
DCn+1
MSB
SDI
tH2
tSU2
tSU2
CLK
1
96
1
192
1
2
DCn-1
MSB
DCn-1
MSB-1
DCn-1
LSB
DCn
MSB
SID
MSB
X
X
SDO
X
Error Information Output
The open-drain output pin XERR indicates if the device is in one of the two error conditions: overtemperature flag or
open LED detect. During normal operation, the internal transistor connected to pin XERR is turned off and the voltage
on XERR is pulled up to VCC through an external pullup resistor.
If an overtemperature or open LED condition is detected, the internal transistor is switched on, and XERR is pulled to
GND. Because XERR is an open-drain output, multiple AS1112 devices can be ORed together and pulled up to VCC
with a single pullup resistor (see Figure 15 on page 15). This reduces the number of signals needed to report a system
error.
To differentiate the overtemperature flag from the open LED detect flag from pin XERR, the open LED detect flag can
be masked out by setting OEN = 1 (see Table 9).
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