Datasheet

Dual Serial UART with 128-Word FIFOs
MAX3109
22 Maxim Integrated
Enable and configure transmitter synchronization with
the TxSynch register. Triggering and synchronization
requires that the transmitters are disabled before the
trigger is received. This can be done by setting the
MODE1[1]: TxDisabl bit high or by using the auto trans-
mitter disable function (TxSynch[4] is logic 1).
Transmitter Synchronization
Synchronize multiple UARTs so that their transmitters
start transmission simultaneously by assigning a com-
mon trigger command to the UARTs that should be
synchronized.
Intrachip and Interchip Synchronization
Intrachip transmitter triggering occurs when the two UARTs
in a MAX3109 device are triggered by one command. This
type of synchronization is supported in both SPI and I
2
C
modes, as the trigger commands are global commands
that are received by both UARTs simultaneously.
Interchip transmitter triggering synchronizes UARTs in
different MAX3109 devices. This type of synchroniza-
tion is achievable in SPI mode only. Pull the CS input of
all the MAX3109 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.
I
2
C protocol does not allow simultaneous addressing of
multiple devices.
Delayed Triggering
A delay can be programmed to postpone the start of
transmission after receiving an assigned trigger com-
mand. Set the delay by programming the SynchDelay1
and SynchDelay2 registers.
Trigger Accuracy
The delay between the time when the MAX3109 receives
a trigger command and the time when the associ-
ated transmitter starts transmission is made up of a fixed,
deterministic portion, and a variable, random component.
Figure 11. Setup and Hold Times in Auto Transceiver Direction Control
Figure 10. Auto Transceiver Direction Control
TX_
FIRST CHARACTER LAST CHARACTER
RTS_
SETUP
HOLD
MAX3109
MAX14840E
TRANSMITTER
TX_
B
A
D
RTS_
RX_
TxFIFO
RECEIVER
AUTO
TRANSCEIVER
CONTROL
RxFIFO
DI
RO
RE
DE
R