MAX14830 datasheet(44/68 Pages) MAXIM

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Maxim Integrated

Quad Serial UART with 128-Word FIFOs

MAX14830

FlowLvl—Flow Level Register

FlowLvl is used for selecting the RxFIFO threshold levels used for software (XON/XOFF) and hardware (RTS/CTS) flow

control.

Bits 7–4: Resume[n]

Resume[n] bits set the Transmit FIFO threshold at which an XON is automatically sent or RTS_ is automatically set low.

This signals the far end station to start transmission. The actual threshold level is calculated as 8 x Resume[n]. The

resulting level is in the range of 0 to 120.

Bits 3–0: Halt[n]

Halt[n] bits set a Receive FIFO threshold level at which an XOFF is automatically sent or RTS_ is automatically set high,

depending on whether automatic software or hardware flow control is enabled. This signals the far end station to halt

transmission. The actual threshold level is calculated as 8 x Halt[n]. Hence the selectable threshold granularity is eight.

The resulting level is in the range of 0 to 120.

FIFOTrigLvl—FIFO Interrupt Trigger Level Register

Bits 7–4: RxTrig[n]

The RxTrig[n] bits allow definition of the Receive FIFO threshold level at which an ISR[3] interrupt is generated. This

can be used to signal that the Receive FIFO is nearing overflow or that a predefined number of FIFO locations are

available for being read out in one block.

The actual FIFO trigger level is 8 x RxTrig[n], hence the selectable threshold granularity is eight.

Bits 3–0: TxTrig[n]

The TxTrig[n] bits allow definition of the Transmit FIFO threshold level at which the MAX14830 generates an ISR[4]

interrupt. This can be used to manage data flow to the Transmit FIFO. For example, if the trigger level is defined near

the bottom of the TxFIFO, the host knows that a predefined number of FIFO locations are available to be written to in

one block. Alternatively, if the trigger level is set near the top of the FIFO, the host is warned when the Transmit FIFO

is nearing overflow, if written to on a word-by-word basis.

The actual FIFO trigger level is 8 x TxTrig[n], hence the selectable threshold granularity is eight.

ADDRESS:

0x0F

MODE:

R/W

BIT

NAME

Resume3

Resume2

Resume1

Resume0

Halt3

Halt2

Halt1

Halt0

RESET

ADDRESS:

0x10

MODE:

R/W

BIT

NAME

RxTrig3

RxTrig2

RxTrig1

RxTrig0

TxTrig3

TxTrig2

TxTrig1

TxTrig0

RESET

MAX14830 Datasheet(PDF) 44 Page - Maxim Integrated Products

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