參數(shù)資料
型號: SCN68681E1F40
廠商: NXP SEMICONDUCTORS
元件分類: 微控制器/微處理器
英文描述: Dual asynchronous receiver/transmitter DUART
中文描述: 2 CHANNEL(S), 1M bps, SERIAL COMM CONTROLLER, CDIP40
文件頁數(shù): 21/28頁
文件大?。?/td> 187K
代理商: SCN68681E1F40
Philips Semiconductors
Product specification
SCN68681
Dual asynchronous receiver/transmitter (DUART)
1998 Sep 04
21
t
CLK
t
CTC
t
Rx
t
Tx
X1/CLK
CTCLK
RxC
TxC
+5V
1K
X1
X2
X2
3.6864MHz
X1
C1
C2
DRIVING FROM
EXTERNAL SOURCE
SCN2681
74LS04
CLOCK
TO OTHER
CHIPS
1K
+5V
CRYSTAL SERIES RESISTANCE3 SHOULD BE LESS THAN 180
R2 = 50k
to 150k
R1: 100K - 1Meg (See design note)
C1 = C2: 0-5pF + (STRAY < 5pF)
t
CLK
t
CTC
t
Rx
t
Tx
OPEN
When using an external clock it is preferred to drive X2 and leave X1 open.
X2 is the input to the internal driver, while X1 is the output.
R1 is only required if U1 will not drive to X2 high level.
Previous specifications indicated X2 should be grounded and X1
should be driven. This is still acceptable. It is electrically easier to drive
the amplifier input than to overdrive its output.
TO THE REST
OF THE DUART
CIRCUITS
R1
U1
R2
SD00115
Figure 9. Clock Timing
NOTES:
1. INTRN or OP3 – OP7 when used as interrupt outputs.
2. The test for open drain outputs is intended to guarantee switching of the output transistor. Measurement of this response is referenced from the mid point of the switching signal, V
M
, to
a point 0.5 volts above V
. This point represents noise margin that assures true switching has occurred. Beyond this level, the effects of external circuitry and test environment are
pronounced and can greatly affect the resultant measurement.
V
M
V
OL
+0.5V
V
OL
CSN
(READ OR
WRITE)
INTERRUPT
1
OUTPUT
t
IR
SD00116
Figure 10. Interrupt Timing
t
TXD
t
TCS
1 BIT TIME
(1 OR 16 CLOCKS)
TxD
TxC
(INPUT)
TxC
(1X OUTPUT)
SD00117
Figure 11. Transmit Timing
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