3

MC2 Chip

The encoding for the interrupt sources is shown in the next table, where IV3-IV0 refer to bits 3-0 of the vector passed during the IACK cycle:

The priority referenced in the following table is established in the MC2 chip logic by implementing a daisy chain request/grant network. There is a similar request/grant daisy chain at the board level.At the board level, the MC2 chip is wired to have the highest priority followed by the IndustryPack interface ASIC (IP2 chip) and then the VMEchip2 ASIC.

Table 3-3. Interrupt Vector Base Register Encoding and

Priority

Interrupt Source 0

IV3-IV0

Daisy Chain Priority

 

 

 

unused

$0 & $1 & $2

..

 

 

 

Timer 4

$3

Lowest

 

 

 

Timer 3

$4

¦

 

 

 

SCSI IRQ

$5

 

 

 

LANC ERR

$6

 

 

 

LANC IRQ

$7

 

 

 

Timer 2

$8

 

 

 

Timer 1

$9

 

 

 

unused

$A

 

 

 

Parity Error

$B

 

 

 

unused

$C & $D

Ø

 

 

 

Serial I/O (Z85230s)

Note 1

Next Highest

 

 

 

ABORT Switch

$E

Highest

 

 

 

unused

$F

..

 

 

 

Note The Z85230 controllers have an integrated interrupt vector register which is separate from the vector generation found on the MC2 chip. The Z85230 also supports a scheme where the base register value is changed based upon the interrupt requested. During the interrupt acknowledge cycle, interrupts from the first Z85230 have priority over those from the second Z85230.

3-14

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Motorola MVME172 manual Interrupt Vector Base Register Encoding Priority, Interrupt Source IV3-IV0 Daisy Chain Priority