UM10562 Datasheet, PDF (472/942 Pages) NXP Semiconductors – LPC408x/407x User manual

NXP Semiconductors
UM10562
Chapter 17: LPC408x/407x UART1
Table 375: Modem status interrupt generation
Enable Modem Status CTSen
CTS Interrupt Delta CTS Delta DCD or Trailing Edge RI Modem Status
Interrupt (U1ER[3]) (U1MCR[7]) Enable (U1IER[7]) (U1MSR[0]) or Delta DSR (U1MSR[3] or
Interrupt
U1MSR[2] or U1MSR[1])
1
1
1
0
0
No
1
1
1
1
x
Yes
1
1
1
x
1
Yes
The auto-CTS function reduces interrupts to the host system. When flow control is
enabled, a CTS1 state change does not trigger host interrupts because the device
automatically controls its own transmitter. Without Auto-CTS, the transmitter sends any
data present in the transmit FIFO and a receiver overrun error can result. Figure 70
illustrates the Auto-CTS functional timing.
UART1 TX
start bits0..7 stop
start bits0..7 stop
start bits0..7 stop
CTS1 pin
Fig 70. Auto-CTS Functional Timing
While starting transmission of the initial character the CTS1 signal is asserted.
Transmission will stall as soon as the pending transmission has completed. The UART will
continue transmitting a 1 bit as long as CTS1 is de-asserted (high). As soon as CTS1 gets
de-asserted transmission resumes and a start bit is sent followed by the data bits of the
next character.
UM10562
User manual
All information provided in this document is subject to legal disclaimers.
Rev. 1 — 13 September 2012
© NXP B.V. 2012. All rights reserved.
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