Sharp MZ-5500 User Manual

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MZ-5600
(iU) VRAM timing
The
following shows various VRAM timings:
.. Display and refresh timings
'JAr
RCS
~
1nW
CPUA
...J
LOAD
______________ ~n~ ______________ _
S/L
--u
CRL
.. Drawing timing
Dot CK
RCS
'rn"
u
Fig. 94
DnW __ ~==~=:~~L- ________________ ~==~==
CPUA -..J
OE ==~======~========~ __ -.
WE L- _______ ..: L-..J
Fig. 95
(iv) VRAM address bus
VRAM address is created by the following logic:
1) The CPU address or the GDC address is selected
setting either output to a high impedance using the
CPUA signal (high for CPU, low for GDC).
2) Switching between row and column addresses is
accomplished by the LS257 for the CPU, and within
the WDC chip for the GDC, both using the RCS
signal (RCS high for A1-A8, low for A9-A14).
CPUA (from VDC1)
ReS
VAO
-r>-
VAI
VA2
WDC
VAS
VA4
VA5
VA6
VA7
VRAM address
A
y VAO
Al B
A9 A
y VAt
A~! B
AS A
Y VA2
All !
y
VAS
MB
At2 A
Y VA4
AS B
AIS A
Y
VAS
A6 B
AI. A
y VAS
A7 B
CPU address bus
AS:
y VA7
LS251 X2
Fig. 96
-68-
(v) Shift register clock
In the 320 dot mode, the internal VDC1· clock is
obtained by halving .the Dot CK S/L for the 640 dot
mode, as shown below:
640 dot mode
dot Ck
S/L----------' r-------------,r-----------
320 dot mode
dot Cl{
S/L
Fig. 97
(vi) CPU ICC8II to VRAM
Al.
AlS
Al7
Al.
The CPU is clocked asynchronously with the GDC. The
VDC1 latches the ~ and ~ from the CPU
and VRAM chip select signal VRAM into itself at the
leading edge of a timing available to the CPU. When a
valid command is transferred from the CPU, the VDC1
performs a read or write operation to the VRAM and,
at the same time, returns a READY to the CPU.
Vcc
11ACK
TO CPU
IOACC ------I
Fig. 98
.. The VRAM output is set low when the CPU address
is COOOOH to EFFFFH.
.. A monostable multivibrator is triggered by the
trailing edge of the READY signal to create the
XACK signal with a pulse width of approximately
200ns.
Dot CK
CPU timing ________ --',
Command lato;---1 I
(into VD Cl i I .... ___ -'.
READY
(Iorwritel
______ ~r-l~ ____________ _
READY
(Ior readl
Fig. 99

Sharp MZ-5500 Specifications

General

Brand	Sharp
Model	MZ-5500
Category	Desktop
Language	English