XR16C854/854D
36
2.97V TO 5.5V QUAD UART WITH 128-BYTE FIFO
REV. 3.1.0
EMSR[5:4]: Extended RTS Hysteresis
TABLE 15: AUTO RTS HYSTERESIS
EMSR[7:6]: Reserved
4.12
FIFO Level Register (FLVL) - Read-Only
The FIFO Level Register replaces the Scratchpad Register (during a Read) when FCTR[6] = 1. Note that this
is not identical to the FIFO Data Count Register which can be accessed when LCR = 0xBF.
FLVL[7:0]: FIFO Level Register
This register provides the FIFO counter level for the RX FIFO or the TX FIFO or both depending on EMSR[1:0].
See Table 14 for details.
4.13
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.
4.14
Device Identification Register (DVID) - Read Only
This register contains the device ID (0x14 for XR16C854). Prior to reading this register, DLL and DLM should
be set to 0x00.
4.15
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.
TABLE 16:
EMSR
BIT-5
EMSR
BIT-4
FCTR
BIT-1
FCTR
BIT-0
RTS#
HYSTERESIS
(CHARACTERS)
0
1
0
1
0
1
0
±4
±6
±8
0
1
0
1
0
1
0
1
±8
±16
±24
±32
1
0
1
0
1
0
1
±40
±44
±48
±52
1
0
1
0
1
0
1
±12
±20
±28
±36