Information

UARTx_WF7816 field descriptions
Field Description
7–0
GTFD
FD Multiplier
Used as another multiplier in the calculation of WT and BWT. This value represents a number between 1
and 255. The value of 0 is invalid. This value is not used in baud rate generation. See Wait time and
guard time parameters and Baud rate generation .
45.3.30 UART 7816 Error Threshold Register (UARTx_ET7816)
The ET7816 register contains fields that determine the number of NACKs that must be
received or transmitted before the host processor is notified. This register may be read at
anytime. This register must be written to only when C7816[ISO_7816E] is not set.
Addresses: UART0_ET7816 is 4006_A000h base + 1Eh offset = 4006_A01Eh
UART1_ET7816 is 4006_B000h base + 1Eh offset = 4006_B01Eh
UART2_ET7816 is 4006_C000h base + 1Eh offset = 4006_C01Eh
Bit 7 6 5 4 3 2 1 0
Read
TXTHRESHOLD RXTHRESHOLD
Write
Reset
0 0 0 0 0 0 0 0
UARTx_ET7816 field descriptions
Field Description
7–4
TXTHRESHOLD
Transmit NACK Threshold
The value written to this field indicates the maximum number of failed attempts (NACKs) a transmitted
character can have before the host processor is notified. This field is meaningful only when
C7816[TTYPE] = 0 and C7816[ANACK] = 1. The value read from this field represents the number of
consecutive NACKs that have been received since the last successful transmission. This counter
saturates at 4'hF and does not wrap around. Regardless of how many NACKs that are received, the
UART continues to retransmit indefinitely. This flag only asserts when C7816[TTYPE] = 0. For additional
information see the IS7816[TXT] field description.
0 TXT asserts on the first NACK that is received.
1 TXT asserts on the second NACK that is received.
3–0
RXTHRESHOLD
Receive NACK Threshold
The value written to this field indicates the maximum number of consecutive NACKs generated as a result
of a parity error or receiver buffer overruns before the host processor is notified. After the counter
exceeds that value in the field, the IS7816[RXT] is asserted. This field is meaningful only when
C7816[TTYPE] = 0. The value read from this field represents the number of consecutive NACKs that have
been transmitted since the last successful reception. This counter saturates at 4'hF and does not wrap
around. Regardless of the number of NACKs sent, the UART continues to receive valid packets
indefinitely. For additional information, see IS7816[RXT] field description.
Chapter 45 Universal Asynchronous Receiver/Transmitter (UART)
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
Freescale Semiconductor, Inc. 1083