Apple Lisa - Page 27

Confidential
Lisa Hardware Reference Manual
The 6522
has two eight bit parallel I/O ports (Peripheral A Port,
or PAO-PA7, and Peripheral B Port, or PBO-PB7). The control lines
for these ports are CAl, CA2, CB1, and CB2. The bit assignment
is as follows:
6522 Peripheral A Port
+----+---
I CD7 I CD6
I ---
PAY PA6
CDO - CD7
CAl
CA2
I -.. .--+-----+---- --+
CDS I CD4 I CD3 I CD2 I CDl CDO I
Lisa Name
I ----+----+---_+_----+----_+_---1-
PAS PA4 PA3 PA2 PAl PAO
Synertek Name
"
Data bus for communication with the cops.
CAl must be programmed as an input that latches the
COPS data in the Peripheral A Port.
CA2 must be programmed to handshake with the COPS
to indicate that the data has been latched.
6522 Peripheral B Port
+= ----+-----+-- . . --t-,--_+_-,---+----+----~__+
I CR/ I CRDY I PRj FDIR I VC2 VCl VCO I ENC I Lisa Name
Tf----~~-----~--~-----+---_+_-- I ----I-
7-Jul-8l
PB7 PB6
PBS PB4
PB3
PB2 PBl PBO
Synertek Name
ENC ENC controls the CVSD Encode/Decode line. When
ENC is high, the CVSD circuit is in encode mode.
VCO - VC2 These bits control the speaker volume. iolhen all
three bits are low, the speaker is at its lowest
volume. As .the three bit number formed by
VCO to VCZ increases in magnitude, the speaker
volume increases.
FDIR Floppy Disk Interrupt Request. Before attempting to
read from the memory shared by the 68000 and the disk
controller, it is necessary to insure that the
floppy disk controller is the source of the level 1
interrupt. If it is not, the attempted memory
access would disturb the disk operation in progress.
The FDIR input allows the disk interrupt line to be
sensed to check this condition. If FDIR is 1, the
controller is the source of the interrupt, so the
68000 can safely read the shared memory.
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