User's guide
11
5.1. General-purpose ports
These ports can be programmed either as a handshake-driven, and as single or as
double buffered port (input, output, or bi-directional) with the direction of each bit
individually programmable. These two ports (ports A-B or C-D of the CIO-32) can also
be linked to form a 16-bit I/O port with handshake. Each port can generate an interrupt
when a specific pattern-recognition is detected. This pattern offers a very large
flexibility for a specific OR/AND condition, the polarity and the transition detection
(state or edge) are independently programmable for each bit-port.
The second port (port B or D of the CIO-32) allows an external access to the first and
second software counter/timers (counter/timers 1-2 or 4-5 of the CIO-32).
To control these capabilities, both ports contain 12 registers. The command and
status registers define the primary port functionalities. Two registers are
employed to
define the port specification and handshake modes. The I/O data is accessed through
the input, output and buffer registers. The data direction, data path polarity and special
I/O control registers allow programming each bit. The pattern-recognition is defined
with the pattern polarity, pattern transition and pattern mask registers.
5.2. Special-purpose port
The function of this port (port E or F of the CIO-32) is defined in accordance with the
role of the general-purpose ports. This port can provide either handshake lines for the
general-purpose ports, either an external access to the third counter/timer
(counter/timers 3 or 6 of the CIO-32) or either conventional I/O lines.
Only three registers (data path polarity, data direction, and special I/O control) are
necessary to control the port C when the general-purpose ports functionalities (ports
A-B or C-D of the CIO-32) have been specified.
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