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Mode 0 Digital I/O
This is the simpler of the two I/O modes and works well for most uses. In mode 0, the handshaking signals Latch
and Acknowledge are not used. When reading any port in input mode, the data at the I/O pins at the time of the read
command is returned.
Mode 1 Digital I/O With Handshaking
In Mode 1, a Latch input and an Acknowledge output signal are provided for handshaking operation. This allows
the external circuit to tell the board when new input data is ready or when it has accepted the current output data,
and it allows the board to tell the external circuit when it has read the current input data and when new output data is
ready. Only Port A may be operated in Mode 1.
In all cases, the starting/resting conditions are Latch input = low, and Acknowledge output = low.
Note: Mode 1 is not currently supported by Diamond Systems Universal Driver software.
Auxiliary Digital I/O
CN12 contains three digital outputs and four digital inputs that can be used either for general purpose digital I/O, or
for A/D and counter/timer functions. The operation of these bits is controlled with various bits in two control
registers.
Outputs
DOUT2/CTROUT2, CN12 pin 28
The function of this pin is determined by OUT2EN, Base+10 bit 5.
DOUT1/SHOUT CN12, pin 30
This pin is always the value written to DOUT1 at Base+1, bit 1.
DOUT0/CTROUT0 CN12, pin 27
The function of this pin is determined by OUT0EN, Base+10, bit 4.
Inputs
DIN3/EXTCLK CN12, pin 31.
This signal may always be read at Base+4, bit 3. It may function as an external clock to control A/D conversion
timing when CLKEN = 1 and CLKSEL = 0, in Base+9.
DIN2/EXTGATE CN12, pin 32.
This signal may always be read at Base+4, bit 2. It may function as an external gate to enable and disable A/D
conversions when GT12EN = 1, in Base+10, bit 0.
DIN1/GATE0 CN12, pin 26.
This signal may always be read at Base+4, bit 1. It may function as an external gate for Counter 0 when GT0EN = 1
in Base+10, bit 2. When used as a gate, it is active high, which means that Counter 0 counts as long as it is high and
does not count when it is low.
Diamond Systems Corporation
Poseidon User Manual
Page 96