ZiLOG Z80 User Manual page 89

,Q WKH LQVWUXFWLRQV
WKH ORZHU KDOI RI WKH DGGUHVV EXV $$ ZKLOH WKH DFFXPXODWRU FRQWHQW
LV WUDQVIHUUHG LQ WKH XSSHU KDOI RI WKH DGGUHVV EXV ,Q DOO UHJLVWHU LQGLUHFW
LQSXW RXWSXW LQVWUXFWLRQV LQFOXGLQJ EORFN ,2 WUDQVIHUV WKH FRQWHQW RI
UHJLVWHU & LV WUDQVIHUUHG WR WKH ORZHU KDOI RI WKH DGGUHVV EXV GHYLFH
DGGUHVV ZKLOH WKH FRQWHQW RI UHJLVWHU % LV WUDQVIHUUHG WR WKH XSSHU KDOI RI
WKH DGGUHVV EXV
&38 &RQWURO *URXS
7DEOH  LOOXVWUDWHV WKH VL[ JHQHUDOSXUSRVH &38 FRQWURO LQVWUXFWLRQV 7KH
NOP
RSHUDWLRQ XQWLO D VXEVHTXHQW LQWHUUXSW LV UHFHLYHG ZKLOH WKH
XVHG WR ORFN RXW DQG HQDEOH LQWHUUXSWV 7KH WKUHH LQWHUUXSW PRGH
FRPPDQGV VHW WKH &38 WR DQ\ RI WKH WKUHH DYDLODEOH LQWHUUXSW UHVSRQVH
PRGHV DV IROORZV ,I 0RGH  LV VHW WKH LQWHUUXSWLQJ GHYLFH FDQ LQVHUW DQ\
LQVWUXFWLRQ RQ WKH GDWD EXV DQG DOORZ WKH &38 WR H[HFXWH LW 0RGH  LV D
VLPSOLILHG PRGH ZKHUH WKH &38 DXWRPDWLFDOO\ H[HFXWHV D UHVWDUW
ORFDWLRQ
FRQWHQW LV SXVKHG RQWR WKH VWDFN  0RGH  LV WKH PRVW SRZHUIXO EHFDXVH LW
DOORZV IRU DQ LQGLUHFW FDOO WR DQ\ ORFDWLRQ LQ PHPRU\ :LWK WKLV PRGH WKH
&38 IRUPV D ELW PHPRU\ DGGUHVV ZKHUH WKH XSSHU HLJKW ELWV DUH WKH
FRQWHQW RI UHJLVWHU , DQG WKH ORZHU HLJKW ELWV DUH VXSSOLHG E\ WKH
LQWHUUXSWLQJ GHYLFH 7KLV DGGUHVV SRLQWV WR WKH ILUVW RI WZR VHTXHQWLDO E\WHV
LQ D WDEOH ZKHUH WKH DGGUHVV RI WKH VHUYLFH URXWLQH LV ORFDWHG 7KH &38
DXWRPDWLFDOO\ REWDLQV WKH VWDUWLQJ DGGUHVV DQG SHUIRUPV D
LQVWUXFWLRQ WR WKLV DGGUHVV
Address of Interrupt
Service Routine
80
 DQG
IN A
LV D GRQRWKLQJ LQVWUXFWLRQ 7KH
VR WKDW QR H[WHUQDO KDUGZDUH LV UHTXLUHG WKH ROG 3&
0038H
  WKH ,2 GHYLFH DGGUHVV Q DSSHDUV LQ
OUT n A
LQVWUXFWLRQ VXVSHQGV &38
HALT
Pointer to Interrupt Table,
Register I is Upper Address,
Peripheral Supplies
Lower Address
= &38 ,QVWUXFWLRQ 'HVFULSWLRQ
< %27
7UGT U /CPWCN

DQG DUH
DI E1
WR
RST
CALL