Motorola MVME1X7P User Manual

Programming Model

http://www.motorola.com/computer/literature

3-33

The Receive PIACK Register is used to execute receive pseudo interrupt 
acknowledge cycles to the CD2401. 

When the Local Bus master initiates a read cycle to this register, the 
PCCchip2 executes an interrupt acknowledge cycle to the CD2401 with 
A7-A0 = $03. (Note that the PILR1 register in the CD2401 should be set 
to the same value ($03) for the interrupt acknowledge cycle to operate 
properly.) 

To finish the local read cycle, the PCCchip2 drives the vector received 
from the CD2401 onto the local data bus, and asserts TA*. Reads to this 
register are termed pseudo interrupt acknowledge cycles because they are 
normal read cycles on the Local Bus side but they are interrupt 
acknowledge cycles on the CD2401 side of the PCCchip2. They are 
necessary to support polled mode operation with the CD2401.

If this register is read when an interrupt is not present, the 
interrupt acknowledge cycle times out with a TEA if the Local 
Bus timer is enabled.

Receive Interrupt vector bits 7-0 reflect the transmit 
interrupt vector driven by the CD2401 to the PCCchip2 
during a pseudo interrupt acknowledge cycle. 

7

6

5

4

3

2

1

0

RIV7

RIV6

RIV5

RIV4

RIV3

RIV2

RIV1

RIV0

R

R

R

R

R

R

R

R

X

X

X

X

X

X

X

X