XR16M564/564D
37
REV. 1.0.0
1.62V TO 3.63V QUAD UART WITH 32-BYTE FIFO
EFR[4]: Enhanced Function Bits Enable
Enhanced function control bit. This bit enables IER bits 4-7, ISR bits 4-5, FCR bits 4-5, MCR bits 5-7, and DLD
to be modified. After modifying any enhanced bits, EFR bit-4 can be set to a LOW to latch the new values. This
feature prevents legacy software from altering or overwriting the enhanced functions once set. Normally, it is
recommended to leave it enabled, HIGH.
Logic 0 = modification disable/latch enhanced features. IER bits 4-7, ISR bits 4-5, FCR bits 4-5, MCR bits 5-
7, and DLD are saved to retain the user settings. After a reset, the IER bits 4-7, ISR bits 4-5, FCR bits 4-5,
and MCR bits 5-7, and DLD are set to a LOW to be compatible with ST16C550 mode (default).
Logic 1 = Enables the above-mentioned register bits to be modified by the user.
EFR[5]: Special Character Detect Enable
Logic 0 = Special Character Detect Disabled (default).
Logic 1 = Special Character Detect Enabled. The UART compares each incoming receive character with
data in Xoff-2 register. If a match exists, the receive data will be transferred to FIFO and ISR bit-4 will be set
to indicate detection of the special character. Bit-0 corresponds with the LSB bit of the receive character. If
flow control is set for comparing Xon1, Xoff1 (EFR [1:0]= ‘10’) then flow control and special character work
normally. However, if flow control is set for comparing Xon2, Xoff2 (EFR[1:0]= ‘01’) then flow control works
normally, but Xoff2 will not go to the FIFO, and will generate an Xoff interrupt and a special character
interrupt, if enabled via IER bit-5.
TABLE 16: SOFTWARE FLOW CONTROL FUNCTIONS
EFR BIT-3
CONT-3
EFR BIT-2
CONT-2
EFR BIT-1
CONT-1
EFR BIT-0
CONT-0
TRANSMIT AND RECEIVE SOFTWARE FLOW CONTROL
0
No TX and RX flow control (default and reset)
0
X
No transmit flow control
1
0
X
Transmit Xon1, Xoff1
0
1
X
Transmit Xon2, Xoff2
1
X
Transmit Xon1 and Xon2, Xoff1 and Xoff2
X
0
No receive flow control
X
1
0
Receiver compares Xon1, Xoff1
X
0
1
Receiver compares Xon2, Xoff2
1
0
1
Transmit Xon1, Xoff1
Receiver compares Xon1 or Xon2, Xoff1 or Xoff2
0
1
Transmit Xon2, Xoff2
Receiver compares Xon1 or Xon2, Xoff1 or Xoff2
1
Transmit Xon1 and Xon2, Xoff1 and Xoff2,
Receiver compares Xon1 and Xon2, Xoff1 and Xoff2
0
1
No transmit flow control,
Receiver compares Xon1 and Xon2, Xoff1 and Xoff2