Samsung S3F80JB SYM System Mode Register DEH Set1 Bank0, Tri-State External Interface Control Bit

Models: S3F80JB

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CONTROL REGISTERSS3F80JB

SYM — System Mode Register

DEH Set1 Bank0

Bit Identifier

Reset Value

Read/Write

Addressing Mode

.7

.6 and .5

.4 – .2

.7

.6

.5

.4

.3

.2

.1

.0

0

x

x

x

0

0

R/W

R/W

R/W

R/W

R/W

R/W

Register addressing mode only

Tri-State External Interface Control Bit (1)

0Normal operation (disable tri-state operation)

1Set external interface lines to high impedance (enable tri-state operation)

Not used for S3F80JB (2)

Fast Interrupt Level Selection Bits (3)

0

0

0

IRQ0

0

0

1

IRQ1

0

1

0

IRQ2

0

1

1

IRQ3

1

0

0

IRQ4

1

0

1

IRQ5

 

 

 

 

1

1

0

IRQ6

 

 

 

 

1

1

1

IRQ7

 

 

 

 

.1

Fast Interrupt Enable Bit (4)

 

0

Disable fast interrupt processing

 

1

Enable fast interrupt processing

.0

Global Interrupt Enable Bit (5)

 

0

Disable global interrupt processing

 

1

Enable global interrupt processing

NOTES:

1.Because an external interface is not implemented for the S3F80JB, SYM.7 must always be "0".

2.Although the SYM register is not used, SYM.5 should always be “0”. If you accidentally write a “1” to this bit during normal operation, a system malfunction may occur.

3.You can select only one interrupt level at a time for fast interrupt processing.

4.Setting SYM.1 to "1" enables fast interrupt processing for the interrupt level currently selected by SYM.2–SYM.4.

5.Following a reset, you must enable global interrupt processing by executing an EI instruction (not by writing a "1" to SYM.0).

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Page 107
Image 107
Samsung S3F80JB manual SYM System Mode Register DEH Set1 Bank0, Tri-State External Interface Control Bit