70
The Control PCA state contains these registers:
Name
Size
Radix
Read-Only
Action
OBUF
16
8
Output buffer
BUSY
2
8
Busy unit 1
CNT
9
8
Check record counter
CMD
1
2
Command flip-flop
CTL
1
2
Control flip-flop
FLG
1
2
Flag flip-flop
FBF
1
2
Flag buffer flip-flop
RARC
8
10
Record address register (cylinder)
RARH
5
10
Record address register (head)
RARS
5
10
Record address register (sector)
CYL [0:1]
8
10
Current cylinder, drives 0-1
HED [0:1]
5
10
Current head, drives 0-1
STA [0:1]
16
8
Drive status, drives 0-1
CTIME
24
10
Data transfer command delay time
DTIME
24
10
Data channel command delay time
STIME
24
10
Seek delay time, per cylinder
XTIME
24
10
Inter-word transfer time
5.3 12606B Disc Memory Interface with One 2770/2771 Disc,
12610B Drum Memory Interface with One 2773/2774/2775 Drum
The 12606B Disc Memory Interface connects one HP 2770A or 2771A fixed-head disc drive to the HP computer
family. The 12610B Drum Memory Interface connects one HP 2773A 2774A, or 2775A fixed-head drum drive.
Both interfaces consist of two Printed Circuit Assemblies installed in adjacent I/O slots. The Data PCA is assigned
the higher-priority (lower numbered) select code, and the Control PCA is assigned the lower-priority select code.
The DRD and DRC devices simulate these PCAs.
The storage capacity of the HP 277x drives is expandable by adding sets of heads to the base model. This
simulation supports the following models and options:
Model-Option
Tracks
Sectors
Words
Capacity
2770A
32
90
64
180 KW
2771A
64
90
64
360 KW
2771A-001
128
90
64
720 KW
2773A
192
32
64
384 KW
2773A-001
256
32
64
512 KW
2773A-002
320
32
64
640 KW
2774A
384
32
64
768 KW
2774A-001
448
32
64
896 KW
2774A-002
512
32
64
1024 KW
2775A
768
32
64
1536 KW
Attaching a disc or drum image file to a unit simulates applying power to the drive:
ATTACH {-R} DRC <image-filename>
