PS081 Datasheet, PDF (74/155 Pages) ams AG – Single Chip Solution for Strain Gauges

PSØ81
4.4.2  Port definition
00 = output
01 = input with pull-up
10 = input with pull-down
11 = input
MULT_IO4 & 05 are set by default as inputs. MULT_IO4 is set to 01 because in PSØ8 this pin is con-
nected to Vcc. This way, the pin compatibility is kept.
4.4.3  Output – write
The outputs are set in configuration register 0 and register 17:
SPI_DO_IO0
Configreg_0, bit 10
io_a[0]
SPI_DI_IO1
Configreg_0, bit 11
io_a[1]
SPI_CLK_IO2
Configreg_0, bit 12
io_a[2]
MULT _IO3
Configreg_0, bit 13
io_a[3]
MULT _IO4
Configreg_17, bit 6
io_a[0]
MULT _IO5
Configreg_17, bit 7
io_a[1]
4.4.4  Increasing the number of Inputs
By means of external diodes, the maximum number of inputs is 21 , as long as no output is used. In
dependency of how many pins you connect, the number of maximum inputs varies. The following table
and illustration show the conection of the inputs. Please note, that in Wheatstone mode there is a
natural reduction of 1 pin, as I/O3 is used to control an external switch in Wheatstone mode.
Table 4.3 Number of I/Os
# of pins
6
5
4
3
# of inputs
21
15
10
6
The combination of 2 input lines gives another input. The 2 lines are connected over diodes electri-
cally. Please see the follwing picture showing the maximum number of combinations (21). The pos-
sibility of increasing the number of inputs makes only sense if you want to have more than 4 inputs,
otherwise you can use Mult_IO 0 to Mult IO 3 directly.
The recognition of synchronously pressed buttons is timing sensitive. Therefore the status register
RAM address 26 to 28 have implemented the following features:
ƒƒ Simultaneously pressed buttons are detected only if the single buttons haven‘t been pressed
before.
acam-messelectronic gmbh - Friedrich-List-Str.4 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de
4-17
Member of the ams Group