Miscellaneous #6
IWM Port Description

Revised by Glenn A. Baxter (November 1988)
Written by Cameron Birse (February 1986)

This Technical Note documents the IWM port pin assignments on various machines.


Apple IIGS Disk Port Pin Assignments

Signal Name
Disk Port Pins (DB-19)
Phase 0
11
Phase 1
12
Phase 2
13
Phase 3
14
/WReq
15
Dr1
17
Rd
18
Wr
19
Wrt Prot
10
Dr2
9
HeadSel
16
Gnd
1,2,3
3.5Disk
4
-12v
5
+5v
6
+12v
7,8

Apple IIe UniDisk 3.5 Controller Disk Port Pin Assignments

Signal Name
Disk Port Pins (DB-19)
Phase 0
11
Phase 1
12
Phase 2
13
Phase 3
14
/WrtReqII
15
/HstEnbl
17
Rd
18
Wr
19
Wrt Prot
10
No Connection
9,16
Gnd
1,2,3,4
-12v
5
+5v
6
+12v
7,8

Apple IIc Disk Port Pin Assignments

Signal Name
Disk Port Pins (DB-19)
Phase 0
11
Phase 1
12
Phase 2
13
Phase 3
14
/WrtReq
15
/Enbl 2
17
Rd
18
Wr
19
Wrt Prot
10
No Connection
16
Gnd
1,2,3,4
-12v
5
+5v
6
+12v
7,8
External Interrupt
9
Note: On the Apple IIc Plus, the disk port pins are driven by a custom ASIC instead of by the IWM chip.

Macintosh Disk Port Pin Assignments

Signal Name
Disk Port Pins (DB-19)
Phase 0
11
Phase 1
12
Phase 2
13
Phase 3
14
/WrtReq
15
/Enbl 2
17
Rd
18
Wr
19
PWM
10
HdSel
16
GND
1,2,3,4
-12v
5
+5v
6
+12v
7,8

This and all of the other Apple II Technical Notes have been converted to HTML by Aaron Heiss as a public service to the Apple II community, with permission by Apple Computer, Inc. Any and all trademarks, registered and otherwise, are properties of their owners.