MAX14830 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_
transmission 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
trigger command is received. Optional delays can also
be programmed, which delay the start of transmission
after a trigger command is received. A UART’s transmit-
ter 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
Tx FIFO
TRANSMITTER ^TX_
DI
D
DE
MAX14830
AUTO
TRANSCEIVER
RTS_
CONTROL
B
MAX14840E
A
RE
Rx FIFO
RECEIVER
RX_ RO
R
Figure 10. Auto Transceiver Direction Control
bits (U0 and 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
trigger command to the UARTs that should be synchro-
nized.
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 commands 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
transmission after the reception of an assigned trig-
ger command. 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
Maxim Integrated
HOLD
LAST CHARACTER
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