Programmable Sound Generator - Sharp MZ-800 Service Manual

MZ-800
Pin name 1/0 Active Signal name
Function
PAD IN L RDA A low on this line indicates that the printer data is ready to receive.
W
PA,
IN L STA A low on this line informs the personal a paper depletion during status check.
u.
PA2 IN
-
GND
~
PA3 IN
-
GND
<{
PA. IN H An 8253 output used for interrupt.
t:
e
PA5 IN H Horizontal blanking signal used for interrupt.
a..
PAs OUT H IRT Used for printer initialization.
PA,
OUT H
RDP
Indicates the printer to receive data.
PB. OUT
-
RD.
PB,
OUT -
RD,
LL
PB2 OUT
-
RD2
U.
~
- PB3 OUT RD3
co
PB.
OUT RD.
Printer data or control code to the printer.
-
t:
PB5 OUT RD5 e -
a..
PB.
OUT RD. -
PB, OUT - RD,
Interfacing timing
CD
@
~ @
RDA
~~~~2~
PBo - PB ,
X
Eff~ctive
data
RDP
I I I
I
I
,
Personal Personal Direct the
After conforming
computer.
computer sends
printer to
high state of
confirms that data to the receive data.
RDA. it makes
RDAis low.
printer.
RDP forced low.
After the personal computer confirms that the printer is
ready to receive data at (<D), the data is then sent to $FF
port (PlO port B) at step
(ID).
As reception of data is directed to the printer at step
(@),
it makes RDP forced low at step
(@)
upon confirm-
ing that the printer received it (RDA=H). After this, it
awaits until RDA goes from high to low before transfer
of a next data. But, it is possible to transfer successive
data by interrupting the CPU at a falling edge of RDA,
since RDA is inputted to the RSTB input of the PlO,
when in the port B mode O.
It is also possible to interrupt the CPU referring to Port A
inputs. Though discussed above is the printer interface
methlod for the MZ compatible printer types, there is the
Centronics compatible method for parallel interfacing of
the printer. Since this method is basically the same as
the MZ mode, except that signal polarity is opposite.
MZ specification
Centronics specification
c----
-------
-
l
Signal name Active Signal name Active
'------------------
-----,--,.
RDA (NOTE)
"L"
BUSY "H"
RDP
"H" STB
"L"
IRT
"H" INPUT PRIME
"L"
34
NOTE: Though RDA is active low, it may be handled
the same as high state of BUSY when consi-
dered in term of signal significance.
As shown in the figure above, it could be known that
RDP and IRT should be inverted in order to make
connection with the Centronics compatible printer.
It can be attained by changing PRSW to high using the
dip switch.
NOTE: When the MZ-800 dedicated printer is used,
there may be such a case that proper operation
is not attained due to different printing charac-
ters and control codes. It must be also noted
that all MZ-800 characters can not be printed.
Besides, connection with a Centronics compati-
ble printer may not be permitted hardware-wise,
sometimes.
4-6. Programmable sound generator
The SN76489N is used for the programmable sound
generator which is controlled by the I/O port $F2. It is
write only. In order to permit smooth sound generation,
timer interrupt is applied using the 8253. For the
interrupt timer, the count 0 of the 8253 is used. The
counter 0 is used for creation of sound steps in the
MZ-700 mode, but, it is used for the timer interrupt
source of the PSG in the MZ-800 mode. Interrupt is
controlled by PA5 of the PlO. it is, however, possible to
mask the counter 0 output by PCO of the 8255, in order
to prevent sound generation during interrupt.
l