IN16C554A Datasheet, PDF (13/31 Pages) IK Semicon Co., Ltd – Independent receiver clock input

IN16C554A
Quadruple UART
February 2009 REV 1.01
External
Clock
Optional
Clock
Output
XTAL1
SB16C554A
XTAL2
XTAL1
R1
CRYSTAL
SB16C554A
C1
C2
R2
XTAL2
Figure 7: Baud Rate Generator Block Diagram
Table 4: Component Values
Frequency Range (MHz)
1.8~8
8~16
C1 (pF)
22
33~68
C2 (pF)
68
33 ~ 68
R1 (Ω)
220K
220K ~ 2.2M
R2(Ω)
470 ~ 1.5K
470 ~ 1.5K
6.3 Break and Time-out Conditions
Break Condition:
Break Condition is occurred when TXD signal outputs ‘0’ and sustains for more than one
character.
It is occurred if LCR[6] is set to ‘1’ and deleted if ‘0’. If break condition is occurred when
normal data are transmitted on TXD, break signal is transmitted and internal serial data
are also transmitted, but they are not outputted to external TXD pin. When Break
condition is deleted, then they are transmitted to TXD pin.
Figure 7 below shows the Break Condition Block Diagram.
Time-out Condition:
When serial data is received from external UART, characters are stored in RX FIFO.
When the number of characters in RX FIFO reaches the trigger level, interrupt is
generated for the CPU to treat characters in RX FIFO. But when the number of characters
in RX FIFO does not reach the trigger level and no more data arrives from external
device, interrupt is not generated and therefore CPU cannot recognize it. IN16C554A
offers time-out function for this situation. Time-out function generates an interrupt and
reports to CPU when the number of RX FIFO is less than trigger level and no more data
receives for four character time.
Time-out interrupt is enabled when IER[2] is set to ‘1’ and can be verified by ISR.
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