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M Z 3500
DO-D7
RXD
WR
RD
C/D
CS
DSR
DTR
RTS
CTS
TXRDY
TXC
TXE
RXC
SYNET/BD
Data Bas
Receive Data (IN/OUT)
Write (IN)
Read (IN)
Control/Data (IN/OUT)
Chip Select (IN)
Data Set Ready (IN)
Data Terminal Ready (OUT)
Request to Send (OUT)
CleartoSend (IN)
Transmitter Ready (OUT)
Transmitter Clock (IN)
Transmitter Empty (OUT)
Receiver Clock (IN)
SYNC Detect/Break Detect (IN/OUT)
Block diagram
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
ränge 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 DI P
• Intel 8253-5 compatible
Pin conf iguration (Top View)
>VCC
JRTJ
3CS
3A1
JAO
3CLK2
JOUT2
5GATE2
3CLK1
+12
QGATE l
\*S~~~
24
^25
^22
^20
18
17
^16
15
_li
WR
frC
AO
»
AI
>
Data bus
buffer
Read/
write
logic
AA
VV
— 1
c*
Y~
Control
word
register
/*-
\r
A-
V
A
V
i
A
V
-N
-V
A
V
A
-V
Counter
# 0
_}
Counter
# 1
«
C L K O
«
G A T E O
»-01:1 o
4
CLK ]
4
G A T K i
_r
Counter
# 2
t
*-
CLK 2
<
G A T E 2
»• Ol;T 2
D7-DO
CLKN
GATEN
OUTN
RD
WR
CS
A1-AO
Vcc
GND
Data Bus (8 bit)
Counter Clock Inputs
Counter Gate Inputs
Counter Outputs
Read Counter
Write Command or Data
Chip Select
Counter Select
+5 Volts
Ground
-76 -
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