ZiLOG Z80 User Manual page 40

< %27
7UGT U /CPWCN

,17(55837 5(63216(
2YHUYLHZ
,QWHUUXSW (QDEOH'LVDEOH
80
$Q LQWHUUXSW DOORZV SHULSKHUDO GHYLFHV WR VXVSHQG &38 RSHUDWLRQ DQG IRUFH
WKH &38 WR VWDUW D SHULSKHUDO VHUYLFH URXWLQH 7KLV VHUYLFH URXWLQH XVXDOO\
LQYROYHV WKH H[FKDQJH RI GDWD VWDWXV RU FRQWURO LQIRUPDWLRQ EHWZHHQ WKH
&38 DQG WKH SHULSKHUDO :KHQ WKH VHUYLFH URXWLQH LV FRPSOHWHG WKH &38
UHWXUQV WR WKH RSHUDWLRQ IURP ZKLFK LW ZDV LQWHUUXSWHG
7KH = &38 KDV WZR LQWHUUXSW LQSXWV D VRIWZDUH PDVNDEOH LQWHUUXSW
,17 DQG D QRQPDVNDEOH LQWHUUXSW 10,  7KH QRQPDVNDEOH LQWHUUXSW
FDQQRW EH GLVDEOHG E\ WKH SURJUDPPHU DQG LV DFFHSWHG ZKHQHYHU D SHULSK
HUDO GHYLFH UHTXHVWV LW 7KLV LQWHUUXSW LV JHQHUDOO\ UHVHUYHG IRU YHU\ LPSRU
WDQW IXQFWLRQV WKDW FDQ EH HQDEOHG RU GLVDEOHG VHOHFWLYHO\ E\ WKH
SURJUDPPHU 7KLV URXWLQH DOORZV WKH SURJUDPPHU WR GLVDEOH WKH LQWHUUXSW
GXULQJ SHULRGV ZKHQ KLV SURJUDP KDV WLPLQJ FRQVWUDLQWV WKDW GR QRW DOORZ
LQWHUUXSW ,Q WKH = &38 WKHUH LV DQ LQWHUUXSW HQDEOH IOLSIORS ,)) WKDW
LV VHW RU UHVHW E\ WKH SURJUDPPHU XVLQJ WKH (QDEOH ,QWHUUXSW (, DQG
'LVDEOH ,QWHUUXSW ', LQVWUXFWLRQV :KHQ WKH ,)) LV UHVHW DQ LQWHUUXSW
FDQQRW EH DFFHSWHG E\ WKH &38
7KH WZR HQDEOH IOLSIORSV DUH ,)) DQG ,))
IFF1
Disables interrupts
from being accepted
7KH VWDWH RI ,)) LV XVHG WR LQKLELW LQWHUUXSWV ZKLOH ,)) LV XVHG DV D WHPSR
UDU\ VWRUDJH ORFDWLRQ IRU ,))
IFF2
Temporary storage
location for IFF1
2YHUYLHZ