Concurrent Technologies RCIM, User Manual

Page: 49 / 102

Functional Description
3-17
PIGs can be used to drive a signal onto a distributed interrupt line, permitting user
software to generate distributed interrupts that are simultaneously delivered to all RCIMs
in an RCIM chain. RCIM III and RCIM II support twelve PIGs (0-11); RCIM I supports
four PIGs (0-3).
The
rcim_pig(4)
man page provides complete information about PIGs.
PIG Device File
1
The device file
/dev/rcim:
N
/pig
is used to access the PIG register on the local
system. This file must be mapped into the address space of a program using
mmap(2)
. By
default, only users with root privileges have access to do this.
On RCIM III and RCIM IV, the PIG register is 12 bits wide, one bit for each PIG. Two
additional registers allow the PIG bits to be set and cleared in a multiprocessor safe
manner. In the
mmap
’ed PIG register page, the set register (PIGS) is at offset 0x10 and the
clear register (PIGC) is at offset 0x20. Setting a PIG generates a distributed interrupt or
external output, depending on how the PIGs are connected. The required length of the
signal depends upon the requirements of the attached device.
If the signal is being fed into an RCIM IV, it must hold any low or high value for at least 1
microsecond before changing to the next state. For an RCIM III the duration held must be
1.5 microseconds.
Distributed PIGs
1
Any or all of the PIGs on an RCIM can be distributed to all systems connected by an
RCIM chain. The source of a distributed PIG may be located on any of the RCIMs in the
chain.
To determine if a specified PIG has its interrupts sent to all connected systems, use one of
the methods described in the section entitled “Obtaining RCIM Values” earlier in this
chapter. See the “Distributed Interrupts” section below for information about setting up
distributed interrupts.
Distributed Interrupts
1
The real heart and power of the RCIM lies in its distributed interrupt system. Each RCIM
can distribute interrupts simultaneously to all systems connected via an RCIM chain.
RCIMs can support up to twelve distributed interrupts (0-11). A diagram of this
functionality and guidelines for setting up distributed interrupts can be found in the section
“Setting up Distributed Interrupts” earlier in this chapter.
Any of the edge-triggered interrupts, real-time clock timers, GPS pulse per second or
programmable interrupt generators on any of the RCIM boards in the chain can be
configured to be distributed. A distributed device file is associated with each of the
distributed interrupts.
RCIM distributed interrupts must be configured on each system attached to the RCIM that
is either broadcasting or intending to receive a distributed interrupt. Distributed interrupts