TC1796
System Units (Vol. 1 of 2)
Interrupt System
User’s Manual 14-1 V2.0, 2007-07
Interrupt, V2.0
14 Interrupt System
The TC1796 interrupt system provides a flexible and time-efficient means for processing
interrupts. This chapter describes the interrupt system for the TC1796. Topics covered
include the architecture of the interrupt system, interrupt system configuration, and the
interrupt operations of the TC1796 peripherals and Central Processing Unit (CPU).
General information is also given about the Peripheral Control Processor (PCP). For
details about that unit, see Chapter 11.
This chapter also discusses the Non-Maskable Interrupt (NMI) (see Section 14.10 on
Page 14-25).
14.1 Overview
An interrupt request can be serviced either by the CPU or by the PCP. These units are
called “service providers”. Interrupt requests are called “service requests” rather than
“interrupt requests” in this document because they can be serviced by either of the
service providers.
Each peripheral unit in the TC1796 can generate service requests. Additionally, the Bus
Control Units, the Debug Unit, the PCP, and even the CPU itself can generate service
requests to either of the two service providers.
As shown in Figure 14-1, each TC1796 unit that can generate service requests is
connected to one or more Service Request Nodes (SRN). Each SRN contains a Service
Request Control Register mod_SRCx, where “mod” is the identifier of the service
requesting unit and “x” an optional index. Two arbitration buses connect the SRNs with
two Interrupt Control Units (ICUs), which handle interrupt arbitration among competing
interrupt service requests, as follows:
• The Interrupt Control Unit (ICU) arbitrates service requests for the CPU and
administers the CPU interrupt arbitration bus.
• The Peripheral Interrupt Control Unit (PICU) arbitrates service requests for the PCP
and administers the PCP interrupt arbitration bus.
The PCP can make service requests directly to itself (via the PICU), or it can make
service requests to the CPU. The Debug Unit can generate service requests to the PCP
or the CPU. The CPU can make service requests directly to itself (via the ICU), or it can
make service requests to the PCP. The CPU Service Request Nodes are activated
through software.
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