XR16L784_08 Datasheet, PDF (24/51 Pages) Exar Corporation – HIGH PERFORMANCE 2.97V TO 5.5V QUAD UART

XR16L784
HIGH PERFORMANCE 2.97V TO 5.5V QUAD UART
REV. 1.2.3
3.1.6 SLEEP [7:0] - (default 0x00)
The 8-bit Sleep register enables each UART separately to enter Sleep mode. Sleep mode reduces power
consumption when the system needs to put the UART(s) to idle. The UART enters sleep mode when there is
no interrupt pending. When all 4 UARTs are put to sleep, the on-chip oscillator shuts off to further conserve
power. In this case, the quad UART is awakened by any of the UART channel on from a receive data byte or a
change on the modem port (CTS#, DSR#, CD# and RI#). The UART is ready after 32 crystal clocks to ensure
full functionality. Also, a special interrupt is generated with an indication of no pending interrupt. Reading INT0
will clear this wake-up interrupt. Logic 0 (default) and logic 1 disable and enable sleep mode respectively.
SLEEP Register
Individual UART Channel Sleep Enable
Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
Rsvd Rsvd Rsvd Rsvd Ch-3 Ch-2 Ch-1 Ch-0
3.1.7 Device Identification and Revision
There are 2 internal registers that provide device identification and revision, DVID and DREV registers. The 8-
bit content in the DVID register provides device identification. A return value of 0x24 from this register indicates
the device is a XR16L784. The DREV register returns a 8-bit value of 0x01 for revision A, 0x02 for revision B
and so on. This information is very useful to the software driver for identifying which device it is communicating
with and to keep up with revision changes.
DVID [7:0] (default 0x24)
Device identification for the type of UART. The upper nibble indicates it is a XR16L78x series with lower nibble
indicating the number of channels.
Examples:
XR16L784 = 0x24
XR16L788 = 0x28
DREV [7:0]
Revision number of the XR16L784. A 0x01 represents "revision-A" with 0x02 for rev-B and so forth.
3.1.8 REGB [7:0] - (default 0x00)
REGB register provides a control for simultaneous write to all 4 UARTs configuration registers or individually.
This is very useful for device intialization in the power up and reset routines.
REGB[0]
REGB[7:1]
Logic 0 (default) write to each UART configuration registers individually.
Logic 1 enables simultaneous write to all 4 UARTs configuration register. Useful during device initializa-
tion.
Reserved
24