MAX14830_15 Datasheet, PDF (23/68 Pages) Maxim Integrated Products – Quad Serial UART with 128-Word FIFOs

MAX14830
Quad Serial UART with 128-Word FIFOs
This occurs as soon as data is present in the Transmit
FIFO. Auto transceiver direction control is enabled
through MODE1[4]: TrnscvCtrl. Figure 10 shows a typical
MAX14830 connection in a RS-485 application.
The RTS_ output can be set high in advance of TX_ trans-
mission by a programmable time period called the setup
time (Figure 11). The setup time is programmed through
HDplxDelay[7:4]. Similarly, the RTS_ signal can be held
high for a programmable period after the transmitter has
completed transmission. The hold time is programmed
through HDplxDelay[3:0].
Transmitter Triggering and Synchronization
The MAX14830 allows synchronization of transmitters so
that selected UARTs start transmitting data when a trig-
ger command is received. Optional delays can also be
programmed, which delay the start of transmission after a
trigger command is received. A UART’s transmitter can be
assigned one of 16 possible SPI/I²C trigger commands.
A trigger command is defined as any of 16 special values
written into the GloblComnd register (see the GloblComnd
section for more information). When a byte is written
into the GloblComnd register, UART select bits (U0 and
Tx FIFO
TRANSMITTER ^TX_
DI _D
DE
B
AUTO
MAX14830 TRANSCEIVER
RTS_
MAX14840E
CONTROL
A
RE
Rx FIFO
RECEIVER
RX_ RO
R
Figure 10. Auto Transceiver Direction Control
U1) are ignored by the MAX14830, and the GloblComnd
applies to all four UARTs. Transmission is initiated when
the MAX14830 receives the assigned SPI/I²C trigger
command if the selected transmitter is initially disabled
and data has been loaded into its TxFIFO.
Enable and configure transmitter synchronization in the
TxSynch register. Triggering and synchronization requires
that the TxFIFOs are disabled before the trigger is
received. This can be done by setting the MODE1[1] bit
to 1 or by utilizing the auto transmitter disable function
(TxSynch[4] is 1).
Transmitter Synchronization
Synchronize multiple UARTs so their transmitters start
transmission simultaneously by assigning a common trig-
ger command to the UARTs that should be synchronized.
Intrachip and Interchip Synchronization
Intrachip transmitter triggering occurs when any of the
four UARTs in a MAX14830 are triggered by one trigger
command. This type of synchronization is supported in
both SPI and I²C modes, as the trigger commands are
global commands that are received by all four UARTs
simultaneously.
Interchip transmitter triggering occurs when the UARTs in
different MAX14830 devices are synchronized. This type
of synchronization is achievable in SPI mode only. Pull
the CS of all the MAX14830 devices on the bus low during
the SPI master’s write trigger command so that the com-
mands are received by all UARTs on the shared SPI bus.
I²C protocol does not allow simultaneous addressing of
multiple devices.
Delayed Triggering
A delay can be programmed for delaying the start of trans-
mission after the reception of an assigned trigger com-
mand. Set the delay by programming the SynchDelay1
and SynchDelay2 registers.
RTS_
SETUP
TX_
FIRST CHARACTER
Figure 11. Setup and Hold times in Auto Transceiver Direction Control
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HOLD
LAST CHARACTER
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