Impulse 3093 - Manual (Page 13)

© Sealevel Systems, Inc. - 11 - DIO-32B User Manual
Relative Addressing vs. Absolute Addressing
The SeaIO API makes a distinction between “absolute” and “relative” addressing
modes. In absolute addressing mode, the Port argument to the API function acts as a
simple byte offset from the base I/O address of the device. For instance, Port #0
refers to the I/O address base + 0; Port #1 refers to the I/O address base + 1.
Relative addressing mode, on the other hand, refers to input and output ports in a
logical fashion. With a Port argument of 0 and an API function meant to output
data, the first (0
th ) output port on the device will be utilized. Likewise, with a Port
argument of 0 and an API function designed to input data, the first (0 th ) input port of
the device will be utilized.
In all addressing modes, port numbers are zero-indexed; that is, the first port is port
#0, the second port is #1, the third #2, and so on.
Direct Hardware Control
In systems where the users program has direct access to the hardware (DOS) the
tables that follow give the mapping and functions that the DIO-32B provides.
Function Available Port Address Hex Port Type
RD A Base + 0
RD B Base + 1
Optically Isolated Input Port
RD/WR C Base + 2
RD/WR D Base + 3
Reed Relay Output Port
RD = Read, RD/WR = Read or Write
Reading the Inputs
The inputs are active Low. If no voltage is applied across one of the differential
inputs it returns a one on that bit. If an AC or DC voltage is applied it returns a zero
on that bit.
Reading the Outputs
The relay ports return the ones complement of the value that is currently being used
to drive the relays.
Writing the Outputs
The output ports are the only ports that can be written. The relays on a standard
DIO-32B are normally open. To close a relay a one must be written to the
appropriate bit.
Register Description
All ports are set to input after reset or power up.
Address Mode D7 D6 D5 D4 D3 D2 D1 D0
Base+0 Input Port A RD PAD7 PAD6 PAD5 PAD4 PAD3 PAD2 PAD1 PAD0
Base+1 Input Port B RD PBD7 PBD6 PBD5 PBD4 PBD3 PBD2 PBD1 PBD0
Base+2 Output Port C RD/WR PCD7 PCD6 PCD5 PCD4 PCD3 PCD2 PCD1 PCD0
Base+3 Output Port D RD/WR PDD7 PDD6 PDD5 PDD4 PDD3 PDD2 PDD1 PDD0
Base+4 RD 0 0 0 0 0 0 0 0
Base+5 Interrupt Status RD/WR IRQEN IRQST 0 0 0 0 IRC1 IRC0