ZiLOG Z80-RIO Operating System User's Manual page 184

CHAPTER 7
DFS
7.1 ZILOG DISK CONTROLLER
The interface from a Zilog Z-80 System to high-speed disk
units consists of an intelligent disk controller in a
module separate from the system, and a high speed serial
interface link from the system to the controller. The
controller contains its own Z-80 CPU, sockets for 8K of ROM (of
which only 3K is currently used), 16K of static RAM, Direct Memory
Access (DMA) control circuitry, the data decode/encode interface
circuitry and miscellaneous control signal interface logic. The
interface is to Caelus Model 206R or similar units. It will
support up to four disk drives with appropriate daisy-chained
cabling.
The software for this configuration makes the disk
appear as another file system, functionally identical
to the ZDOS file system which exists for the floppy disks.
The Disk File System (DFS) software is capable of running in
two versions. On the MCZ 1/20, the system is bootstrapped from
the floppy disks as a standard system. The system resident
portion of DFS must be loaded from ZDOS by the command ACTIVATE
$DFS. ZDOS is at 2AOO, immediately above the console driver
for RIO, and DFS is placed at the top of memory.
DFS contains an entry point for DISK, the low level
disk controller used by some utilities; it is 2 greater
than the entry point for DFS, and should be activated
with an address at the same time DFS is activated,
thus:
ACTIVATE $DFS;X
*
$DISK E002
If DFS is to be run as the master device, then the command
MASTER $DFS should follow these. At this point ZDOS can be
deactivated, thus effecting a large savings in memory space,
unless it is needed for transfers to diskette.
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