ST16C654 EXAR [Exar Corporation], ST16C654 Datasheet - Page 26

• Manufacturer Part Number: ST16C654
• Description: 2.97V TO 5.5V QUAD UART WITH 64-BYTE FIFO
• Manufacturer: EXAR [Exar Corporation]

   
IER[7]: CTS# Input Interrupt Enable (requires EFR[4]=1)
The UART provides multiple levels of prioritized interrupts to minimize external software interaction. The
Interrupt Status Register (ISR) provides the user with six interrupt status bits. Performing a read cycle on the
ISR will give the user the current highest pending interrupt level to be serviced, others are queued up to be
serviced next. No other interrupts are acknowledged until the pending interrupt is serviced. The Interrupt
Source Table,
associated with each of these interrupt levels.
4.4
4.4.1
4.4.2
Logic 0 = Disable the CTS# interrupt (default).
Logic 1 = Enable the CTS# interrupt. The UART issues an interrupt when CTS# pin makes a transition from
low to high (if enabled by EFR bit-7).
LSR is by any of the LSR bits 1, 2, 3 and 4.
RXRDY is by RX trigger level.
RXRDY Time-out is by a 4-char plus 12 bits delay timer.
TXRDY is by TX trigger level or TX FIFO empty.
MSR is by any of the MSR bits 0, 1, 2 and 3.
Receive Xoff/Special character is by detection of a Xoff or Special character.
CTS# is when the remote transmitter toggles the input pin (from low to high) during auto CTS flow control.
RTS# is when its receiver toggles the output pin (from low to high) during auto RTS flow control.
LSR interrupt is cleared by a read to the LSR register (LSR bits 1-4 will clear but LSR bit-7 will not clear until
character(s) that generated the interrupt(s) has been emptied or cleared from FIFO).
RXRDY interrupt is cleared by reading data until FIFO falls below the trigger level.
RXRDY Time-out interrupt is cleared by reading RHR.
TXRDY interrupt is cleared by a read to the ISR register or writing to THR.
MSR interrupt is cleared by a read to the MSR register.
Xoff interrupt is cleared by a read to ISR.
Special character interrupt is cleared by a read to ISR register or after next character is received.
RTS# and CTS# flow control interrupts are cleared by a read to the MSR register.
Interrupt Status Register (ISR) - Read-Only
Interrupt Generation:
Interrupt Clearing:
Table
11, shows the data values (bit 0-5) for the interrupt priority levels and the interrupt sources
26
2.97V TO 5.5V QUAD UART WITH 64-BYTE FIFO
ST16C654/654D
REV. 5.0.0