CHAPTER 9 MINIMUM HARDWARE CONSIDERATIONS

This chapter discusses the major hardware consideration differences between the 8XC196Lx and the 8XC196Kx. The 8XC196Lx has implemented a reset source SFR that reveals the source of the most recent reset request.

9.1IDENTIFYING THE RESET SOURCE

The reset source (RSTSRC) register indicates the source of the last reset that the microcontroller encountered (Figure 9-1). If more than one reset occurs at the same time, all of the corresponding RSTSRC bits are set. Reading this SFR clears all the register bits.

RSTSRC

Address:

1F92H

 

Reset State:

XXH(1)

The reset source (RSTSRC) register indicates the source(s) of the last reset that the microcontroller encountered.

7

 

 

 

 

0

CFDRST WDTRST SFWRST EXTRST

Bit

Bit

Function

Number

Mnemonic

 

 

 

 

7:4

Reserved; for compatibility with future devices, write zeros to these bits.

 

 

 

3

CFDRST

Clock Failure Detection Reset

 

 

When set, this bit indicates that a failed clock caused the last reset.

 

 

 

2

WDTRST

Watchdog Timer Reset

 

 

When set, this bit indicates that the watchdog timer caused the last reset.

 

 

 

1

SFWRST

Software Reset

 

 

When set, this bit indicates that either the RST instruction or the IDLPD

 

 

instruction used with an illegal key caused the last reset.

 

 

 

0

EXTRST

External Reset

 

 

When set, this bit indicates that the RESET# pin being asserted caused the

 

 

last reset.

 

 

 

NOTE:

 

 

1.The State of the RSTSRC register is inderterminate on a VCC power up condition. All other reset states will have the corresponding reset event bit set in the register.

Figure 9-1. Reset Source (RSTSRC) Register

9-1

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Intel 87C196CA, 8XC196Jx, 8XC196Lx, 8XC196Kx user manual Minimum Hardware Considerations, Identifying the Reset Source