Organization of banks
The digital bank has a total of 24 I/O lines. The lines are configured into three
groups: ports A, B and C, each group consisting of 8 bits. Any of the lines at ports
A, B or C can be configured individually as inputs or outputs.
Ports A and B are connected to a 20-pin header on the HDC-Multiport cable. Port C
is connected to a 10-pin header at J6. The Digital I/O Cable (part #6394) connects
to J6.
Figure 10–2
Organization of banks
connectors
I/O
Port addressing
Ports A, B, C and the control register are addressable. The base I/O address is fixed
at 120h. Digital I/O always uses [base through base +3]. Ports A, B, C and the
control register are addressable, with reference to the base address.
Table 10–3 Digital I/O port address
Port I/O
Address
A
B
C
Control
Register
Base address (120h)
Base a 1 (121h)
Base a 2 (122h)
Base a 3 (123h)
B a s e
B a s e + 1
a s e + 2
a s e + 3
B
B
A
B
C
8
8
8
or
or
or
20-pin connector on
Multiport cable
10-pin connector at J6
Control
Register
71
