Apple Lisa - Page 46

Confidential
Lisa Hardware Reference Manual
THE HARD DISK INTERFACE
The hard disk interface is a general purpose eight bit parallel port
which can be used to connect the Pippin hard disk controller to the
Lisa. The Pippin is a 5-1/4 inch Winchester-type disk capable of
storing about five megabytes of data. The 6522 which connects the
interface to the 68000 bus also provides the programmable baud rate
to the serial ports and generates the slow data bus that latches data
for transfer to the contrast control latch.
DDO - DD7
RW
P~TY/
PSTRB/
CMD/
BSY/
OCD
GRES/
M3
HARD DISK INTERFACE SIGNAL LINES
Disk Data lines. These eight bi-directional
lines communicate data to and from the disk.
Read/Write. RW controls the direction that
data flows on the Disk Data lines. When RW
is high, data moves from the disk to the Lisa.
When RW is low, data moves from the Lisa to
the disk.
This bit contains odd parity on the data being
transmitted. If any parity errors are caught,
the data can be retransmitted.
Processor Strobe ~ine. PSTRB controls the data
flow from the Lisa to .the disk interface. The
timing diagram is given below.
The
Command line tells the disk controller that
there is a command present.
The Busy line is high when the disk controller
is busy. BSY/ is also used as a handshake line
with the CMD/ signal.
Open Cable Detect. If the disk controller is
connected to the Lisa, the oeo line is low.
If the controller is not connected, OCD is
pulled high.
Controller Reset. This line is driven by the CR/
bit (PB7) in the keyboard 6522. In addition, when
the port is used as a general purpose parallel port,
CRES/ is an input which can be read on the keyboard
6522
PRJ bit if the CR/ bit is 1.
M3 is an input that produces the M3 keycode. It
provides a keyboard interrupt which the general
purpose parallel port can use.
Page 46
7-Jul-81