HMS AnyBus DataTransfer Design Manual page 22

INTERRUPT mode
The following flow chart shows the necessary procedure for accessing the DPRAM in interrupt mode.
START
APP_IND = 02
WAIT for
INTERRUPT
AB_IND
=
0F
No
AB_IND
=
F2
No
Yes
ACCESS
DPRAM
APP_IND = 01
WAIT for
INTERRUPT
AB_IND
=
FF
No
AB_IND
=
01
No
Yes
STOP
Figure 7. Interrupt mode
Yes
Yes
HMS F
IELDBUS
DPRAM accessing
in INTERRUPT mode
request control
over DPRAM
wait until DT module
responds
ERROR encountered?
retry
request OK?
if data was written
wrong to the DPRAM;
an other INTERRUPT
will occur!
read output data,clear
new data flag (3fd);
write input data;
access time max. 1 sec.
request release
the DPRAM
wait until DT module
responds
ERROR encountered;
retry release
release OK?
accessing DPRAM
completed
S AB
YSTEMS
Design Guide
Revision 1.12
1998-08-12
Page 22 (35)