8.4.7Priority Mask Register (PRIMSK, Offset 2Ah) (Slave Mode)

The format of the Priority Mask Register is shown in Figure 8-23.The Priority Mask Register provides the value that determines the minimum priority level at which maskable interrupts can generate an interrupt.

Figure 8-23 Priority Mask Register (PRIMSK, offset 2Ah)

15

7

0

Reserved

PRM2

PRM1

PRM0

The value of the PRIMSK Register at reset is 0007h.

Bits 15–3: Reserved

Bits 2–0: Priority Field Mask (PRM2–PRM0) —This field determines the minimum priority which is required for a maskable interrupt source to generate an interrupt.

A value of seven (111b) allows all interrupt sources that are not masked to generate interrupts. A value of five (101b) allows only unmasked interrupt sources with a programmable priority of zero to five (000b to 101b) to generate interrupts.

Table 8-6 Priority Field Mask (Slave Mode)

Priority

PR2–PR0

 

 

(High) 0

0 0 0b

 

 

1

0 0 1b

 

 

2

0 1 0b

 

 

3

0 1 1b

 

 

4

1 0 0b

 

 

5

1 0 1b

 

 

6

1 1 0b

 

 

(Low) 7

1 1 1b

 

 

8-34

Interrupt Control Unit

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AMD Am186TMER, Am188TMER Priority Mask Register PRIMSK, Offset 2Ah Slave Mode, Priority Field Mask Slave Mode PR2-PR0