ZiLOG System 8000 Hardware Reference Manual page 109

HRM Zilog HRM
4.5.2. Winchester Disk Controller: The Disk Controller
controls the fully buffered transfer of data between the CPU
(host) and a selected disk drive. The block diagram in Fig-
ure 4-3 shows the relationship between the controller and
both the ZBI and the disk drives. All transactions between
the controller and the host pass through connectors P1 and
J13 and over the ZBI. Transactions between the controller
and a selected disk drive pass through connectors P2 and
J23, the drive bus. The signals on connector P1 are the
standard ZBI signals; the signals on P2 are common to only
slot three on the back plane. Table 4-13 lists the inter-
face signals between the disk controller and the disk
drives. .
4.5.2.1 CPU Interface: The CPU communicates with the con-
troller through 16 8-bit command registers and an 8-bit
command-status (CIS) register (Figure 4-4). Each register
has a specific command assignment and a specific address.
The CPU writes commands into command registers xxOO through
x
x0F ; the con t roll err e ad s the s ere g is t e r san d per f
0
r~m
s the
specified commands. The controller places the results or
status of the specified command in the CiS register which
the CPU reads. Table 4-14 lists the command and CiS regis-
ter s.
The command and CiS registers reside in the CPU's IIO space
on any 256-word boundary. Within this 256-word block, the
command registers are at "relative addresses xxOO to xxOF
hexadecimal and the CIS register at address xx10. The two
most significant hex values of the address, xx, can be set
by j urn per son the c () nt roll e r boa rd. Ta b
1
e 4- 15
1
i s t s the
jumpers and the bits (15 through 8) that the jumpers con-
trol. This scheme allows more than one controller within
the same IIO space.
Figure 4-5 shows a segMent of IIO space, containing three
256-word blocks. The two most significant hexadecimal nib-
bles (AA, BE, and CC) of the addresses can be set by using
the jumpers listed in Table 4-15. For example, in the
address AAOO, if AA is to equal FF hex, then no jumper is
connected in any of the jumper groups, and all the lines are
high. When a jumper is connected in any jumper group, the
jumper shorts its associated line to ground, a low level.
The controller can accommodate either 2716 or 2732 EPROMs.
Jumpers on the control:er board permit the selection of both
the type of EPROM and any necessary wait states.
Tabl~
4-16
lists the jumpers for memory selections.
4-16
Zilog
4-16