Measurement-computing COM232/8AT Instrukcja Użytkownika Pobierz pdf (Strona 10)

10 COM232/8AT User’s Guide March 1998 1000-0901, rev 1.1

Character Timeout (FIFO Mode only) − Indicates no characters have been removed from, or input to

the receiver FIFO for the last four character times and that there is at least one character in the FIFO

during this time. The interrupt is cleared by reading the receiver FIFO.

Transmitter Holding Register Empty − Indicates that the transmitter holding register is empty. The

interrupt is cleared by reading the interrupt identification register, or by writing to the transmitter

holding register.

MODEM Status − Indicates Clear To Send, Data Set Ready, Ring Indicator, or Data Carrier Detect

have changed state. The interrupt is cleared when the MODEM Status Register is read.

FIFO Control Register

The bit definitions for the FIFO Control Register are as follows:

FIFO Control Register Definitions

D7 RXT1 RXT0 and RXT1 are Receiver Trigger Levels

D6 RXT0

D5 x

D4 x

D3 DMAM DMA Mode Select

D2 XRST Transmit FIFO Reset

D1 RRST Receive FIFO Reset

D0 FE FIFO Enable

RXT0 & RXT1 Receiver FIFO Trigger Levels − Determines the trigger level for the FIFO interrupt as

indicated in the following table.

FIFO Trigger Levels

RXT1 RXT0 Trigger Level

(bytes)

00 1

00 4

10 8

11 14

DMAM DMA Mode Select − Selects the mode of the RxRDY and TxRDY outputs. Note that the

DMA mode is not supported on the RW-100T.

XRST Transmit FIFO Reset − When set (logic 1), all bytes in the transmitter FIFO are cleared and the

counter is reset. The shift register is not cleared. XRST is self-clearing.

RRST Receive FIFO Reset − When set (logic 1), all bytes in receiver FIFO are cleared and the counter

is reset. The shift register is not cleared. RRST is self-clearing.

FE FIFO Enable − When set (logic 1), enables transmitter and receiver FIFOs. When cleared

(logic 0), all bytes in both FIFOs are cleared. This bit must be set when other bits in the FIFO control

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 ... 19 20

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Measurement-computing COM232/8AT Instrukcja Użytkownika Strona 10