XR19L220_07 Datasheet, PDF (29/43 Pages) Exar Corporation – SINGLE CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER

XR19L220
REV. 1.0.1
SINGLE CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
4.12 Baud Rate Generator Registers (DLL and DLM) - Read/Write
The concatenation of the contents of DLM and DLL gives the 16-bit divisor value which is used to calculate the
baud rate:
• Baud Rate = (Clock Frequency / 16) / Divisor
See MCR bit-7 and the baud rate table also.
4.13 Device Identification Register (DVID) - Read Only
This register contains the device ID (0x01 for XR19L220). Prior to reading this register, DLL and DLM should
be set to 0x00.
4.14 Device Revision Register (DREV) - Read Only
This register contains the device revision information. For example, 0x01 means revision A. Prior to reading
this register, DLL and DLM should be set to 0x00.
4.15 Enhanced Feature Register (EFR)
Enhanced features are enabled or disabled using this register. Bit 0-3 provide single or dual consecutive
character software flow control selection (see Table 10). When the Xon1 and Xon2 and Xoff1 and Xoff2 modes
are selected, the double 8-bit words are concatenated into two sequential characters. Caution: note that
whenever changing the TX or RX flow control bits, always reset all bits back to logic 0 (disable) before
programming a new setting.
EFR[3:0]: Software Flow Control Select
Single character and dual sequential characters software flow control is supported. Combinations of software
flow control can be selected by programming these bits.
EFR BIT-3
CONT-3
0
0
1
0
1
X
X
X
1
0
1
0
TABLE 10: SOFTWARE FLOW CONTROL FUNCTIONS
EFR BIT-2
CONT-2
EFR BIT-1
CONT-1
EFR BIT-0
CONT-0
TRANSMIT AND RECEIVE SOFTWARE FLOW CONTROL
0
0
0
No TX and RX flow control (default and reset)
0
X
X
No transmit flow control
0
X
X
Transmit Xon1, Xoff1
1
X
X
Transmit Xon2, Xoff2
1
X
X
Transmit Xon1 and Xon2, Xoff1 and Xoff2
X
0
0
No receive flow control
X
1
0
Receiver compares Xon1, Xoff1
X
0
1
Receiver compares Xon2, Xoff2
0
1
1
Transmit Xon1, Xoff1
Receiver compares Xon1 or Xon2, Xoff1 or Xoff2
1
1
1
Transmit Xon2, Xoff2
Receiver compares Xon1 or Xon2, Xoff1 or Xoff2
1
1
1
Transmit Xon1 and Xon2, Xoff1 and Xoff2,
Receiver compares Xon1 and Xon2, Xoff1 and Xoff2
0
1
1
No transmit flow control,
Receiver compares Xon1 and Xon2, Xoff1 and Xoff2
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