NS32FX164AV-25 National Semiconductor, NS32FX164AV-25 Datasheet - Page 30

• Manufacturer Part Number: NS32FX164AV-25
• Description: IC IMAGING COMM SGNL PROC PLCC68
• Manufacturer: National Semiconductor

Specifications of NS32FX164AV-25

• Processor Type: Advanced Imaging/Communications Signal Processor SIAP™
• Speed: 50MHz
• Voltage: 5V
• Mounting Type: Surface Mount
• Package / Case: 68-PLCC
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Features: -
• Other names: *NS32FX164AV-25; Q1284286

3 0 Functional Description
3 2 2 Returning from an Exception Service Procedure
To return control to an interrupted program one of two in-
structions can be used RETT (Return from Trap) and RETI
(Return from Interrupt)
RETT is used to return from any trap or non-maskable inter-
rupt service procedure Since some traps are often used
deliberately as a call mechanism for supervisor mode proce-
dures RETT can also adjust the Stack Pointer (SP) to dis-
card a specified number of bytes from the original stack as
surplus parameter space
FIGURE 3-4 Interrupt Dispatch and Cascade Tables
(Continued)
30
ures 3-7 and 3-8 show the RETT and RETI instruction flows
RETI is used to return from a maskable interrupt service
procedure A difference of RETT RETI also informs the on-
chip ICU as well as any external interrupt control logic that
interrupt service has completed Since interrupts are gener-
ally asynchronous external events RETI does not discard
parameters from the stack
Both of the above instructions always restore the Program
Counter (PC) and the Processor Status Register from the
interrupt stack If the Direct-Exception mode is disabled
they also restore the MOD and SB register contents Fig-
when the Direct-Exception mode is disabled
TL EE 11267 – 13