SCN2681T Datasheet, PDF (9/14 Pages) NXP Semiconductors – Dual asynchronous receiver/transmitter DUART

Philips Semiconductors
Dual asynchronous receiver/transmitter (DUART)
Product specification
SCN2681T
X1/CLK
CTCLK
RxC
TxC
t_CLK
t_CTC
t_Rx
t_Tx
t_CLK
t_CTC
t_Rx
t_Tx
DRIVING FROM
EXTERNAL SOURCE
OPEN
X1
+5V
R1: 100K - 1Meg (See design note)
C1 = C2: 0-5pF + (STRAY < 5pF)
+5V
1K
74LS04
CLOCK
TO OTHER
CHIPS
SCN2681
X1
TO THE REST
OF THE DUART
CIRCUITS
C1
R2
R1
1KΩ
C2
When using an external clock it is preferred to drive X2 and leave X1 open. _U1
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.
X2
X2
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.
3.6864MHz
CRYSTAL SERIES RESISTANCE3 SHOULD BE LESS THAN 180Ω
R2 = 50kΩ to 150kΩ
Figure 7. Clock Timing
SD00091
SYMBOL
PARAMETER
X1/CLK high or low time
t_CLK
f_CLK
t_CTC
f_CTC
t_RX
f_RX
t_TX
f_TX
X1/CLK frequency
CTCLK (IP2) high or low time
CTCLK (IP2) frequency¹
RxC high or low time
RxC frequency (16X)¹
(1X)¹
TxC high or low time
TxC frequency (16X)¹
(1X)¹
NOTE:
1. Minimum frequencies are not tested but are guaranteed by design.
1 BIT TIME
(1 OR 16 CLOCKS)
TxC
(INPUT)
t_TXD
TxD
LIMITS
Min
Typ
Max
90
2
4
55
0
8
55
0
3.6864
8
0
1
110
0
4
0
1
UNIT
ns
MHz
ns
MHz
ns
MHz
MHz
ns
MHz
MHz
TxC
(1X OUTPUT)
t_TCS
Figure 8. Transmit
SYMBOL
t_TXD
t_TCS
PARAMETER
TxD output delay from TxC external clock input on IP pin
Output delay from TxC low at OP pin to TxD data output
SD00103
LIMITS
Min
Max
300
0
100
UNIT
ns
ns
1998 Sep 04
9