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M
Z
3500
DO~D7
Data
Bas
RXD
Receive
Data
(IN/OUT)
WR
Write
(IN)
RD
Read
(IN)
C/D
Control/Data
(IN/OUT)
CS
Chip
Select
(IN)
DSR
Data
Set
Ready
(IN)
DTR
Data
Terminal
Ready
(OUT)
RTS
Request
to
Send (OUT)
CTS
Clear
to
Send (IN)
TXRDY
.
Transmitter
Ready
(OUT)
TXC
Transmitter
Clock
(IN)
TXE
.
Transmitter
Empty
(OUT)
RXC
.
Receiver
Clock (IN)
SYNET/BD
:
SYNC Detect/Break Detect
(IN/OUT)
2)
UPD8253C-5 (Programmable
Interval
Timer)
The
UPD8253-5
is a
programmable
counter/timer
speci-
fically
designed
for the
8-bit
microcomputer
system.
It
consists
of
three
sets
of
16-bit
counters
that
operate
under
a
maximum counter rate
of
4MHz.
Timer
and six
operational modes
are
programmed
to be
used
for a
wide
range
of
microcomputer system
timing
control.
Features
•
Z-80 compatible
•
Three
sets
of
16-bit
counters
•
DC-4MHz
of
count
rate
•
Programmable
six
operational
modes
and
timer
duration
•
Choice
of
binary
counter/BCD
counter
•
N-channel MOS,
input/output
TTL
compatible
•
Single
+5V
supply,
24-pin
DIP
•
Intel 8253-5 compatible
Pin
configuration
(Top View)
.VCC
Block
diagram
UO
O
wl —
»<:
AO
1
Al >
Data
bus
buffer
Read/
write
logic
c- ^
AA
v-v
^
Control
word
register
1
—
/" '
**w 1
Internal
£
VV
/«-
\r
-N
,V
Counter
# 0
_t
Counter
# 1
•«
t 1 KO
<l
C.MtO
'
*-"n
o
< C 1 K 1
< OA1 ^ 1
»-()l
I 1
t
A^S
S —
K]
Counter
# 2
t
*- Cl K2
«
GA1L2
KHT2
D7-DO
Data
Bus (8
bit)
CLKN Counter Clock Inputs
GATEN Counter
Gate
Inputs
OUTN
Counter Outputs
RD
.
Read
Counter
WR
Write Command
or
Data
CS
Chip
Select
A1~AO
:
Counter Select
Vcc
. +5
Volts
GND
.
Ground
-
76
-