Information

UARTx_IS7816 field descriptions (continued)
Field Description
5
BWT
Block Wait Timer Interrupt
Indicates that the block wait time, the time between the leading edge of first received character of a block
and the leading edge of the last character the previously transmitted block, has exceeded the
programmed value. This flag asserts only when C7816[TTYPE] = 1.This interrupt is cleared by writing 1.
0 Block wait time (BWT) has not been violated.
1 Block wait time (BWT) has been violated.
4
INITD
Initial Character Detected Interrupt
Indicates that a valid initial character is received. This interrupt is cleared by writing 1.
0 A valid initial character has not been received.
1 A valid initial character has been received.
3
Reserved
This read-only field is reserved and always has the value zero.
2
GTV
Guard Timer Violated Interrupt
Indicates that one or more of the character guard time, block guard time, or guard time are violated. This
interrupt is cleared by writing 1.
0 A guard time (GT, CGT, or BGT) has not been violated.
1 A guard time (GT, CGT, or BGT) has been violated.
1
TXT
Transmit Threshold Exceeded Interrupt
Indicates that the transmit NACK threshold has been exceeded as indicated by
ET7816[TXTHRESHOLD]. Regardless of whether this flag is set, the UART continues to retransmit
indefinitely. This flag asserts only when C7816[TTYPE] = 0. If 7816E is cleared/disabled, ANACK is
cleared/disabled, C2[TE] is cleared/disabled, C7816[TTYPE] = 1, or packet is transferred without
receiving a NACK, the internal NACK detection counter is cleared and the count restarts from zero on the
next received NACK. This interrupt is cleared by writing 1.
0 The number of retries and corresponding NACKS does not exceed the value in
ET7816[TXTHRESHOLD].
1 The number of retries and corresponding NACKS exceeds the value in ET7816[TXTHRESHOLD].
0
RXT
Receive Threshold Exceeded Interrupt
Indicates that there are more than ET7816[RXTHRESHOLD] consecutive NACKS generated in response
to parity errors on received data. This flag requires ANACK to be set. Additionally, this flag asserts only
when C7816[TTYPE] = 0. Clearing this field also resets the counter keeping track of consecutive NACKS.
The UART will continue to attempt to receive data regardless of whether this flag is set. If 7816E is
cleared/disabled, RE is cleared/disabled, C7816[TTYPE] = 1, or packet is received without needing to
issue a NACK, the internal NACK detection counter is cleared and the count restarts from zero on the
next transmitted NACK. This interrupt is cleared by writing 1.
0 The number of consecutive NACKS generated as a result of parity errors and buffer overruns is less
than or equal to the value in ET7816[RXTHRESHOLD].
1 The number of consecutive NACKS generated as a result of parity errors and buffer overruns is
greater than the value in ET7816[RXTHRESHOLD].
Memory map and registers
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
1082 Freescale Semiconductor, Inc.