C8051F045 View Datasheet(PDF) - Silicon Laboratories

Part Name

Description

Manufacturer

C8051F045

Mixed Signal ISP Flash MCU Family

Silicon Laboratories 

SFRNEXT

popped to

SFRPAGE

C8051F040/1/2/3/4/5/6/7

SFR Page 0x02

Automatically

popped off of the

stack on return from

interrupt

0x0F

(Port 5)

SFRPAGE

SFRNEXT

SFRLAST

Figure 12.8. SFR Page Stack Upon Return From ADC2 Window Interrupt

Note that in the above example, all three bytes in the SFR Page Stack are accessible via the SFRPAGE,

SFRNEXT, and SFRLAST special function registers. If the stack is altered while servicing an interrupt, it is

possible to return to a different SFR Page upon interrupt exit than selected prior to the interrupt call. Direct

access to the SFR Page stack can be useful to enable real-time operating systems to control and manage

context switching between multiple tasks.

Push operations on the SFR Page Stack only occur on interrupt service, and pop operations only occur on

interrupt exit (execution on the RETI instruction). The automatic switching of the SFRPAGE and operation

of the SFR Page Stack as described above can be disabled in software by clearing the SFR Automatic

Page Enable Bit (SFRPGEN) in the SFR Page Control Register (SFRPGCN). See SFR Definition 12.1.

Rev. 1.5

141

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