Intel MD566X manual Interrupt Enable Register IER, Transmitter Holding Register THR

56K V.92 Data, Fax, and Voice Chipset

Bit 0

Interrupt Pending–This bit indicates when a modem interrupt is pending. Whenever this bit is equal to “0”, then one or more interrupts are pending. Whenever this bit is equal to “1”, then no interrupts are pend- ing. When an interrupt has occurred, the host can determine the cause of the interrupt by looking at the IIR interrupt ID bits 0 and 1 (and interrupt ID bit 2 for FIFO mode).

10.1.8 Interrupt Enable Register (IER)

Register 1

(DLAB = 0)

0

0

0

0

MSIE

RLSIE

THREIE

RDAIE

This register is used to enable up to five types of UART interrupts: receiver line status, received data available, character time-out indication (FIFO mode only), Transmitter Holding register empty, and modem status. Each enabled interrupt can individually cause an interrupt to host on the ∝P HINT output pin. To cause an interrupt to the host (HINT), both the interrupt enable bit and OUT2 (MCR2) must be set

to ‘1’.

Bits 7:4	Not used–These bits are permanently set to “0”.
Bit 3	MSIE (Modem Status Interrupt Enabled)–when set to “1”, this bit enables the modem status interrupt.
Bit 2	RLSIE (Receiver Line Status Interrupt Enabled)–when set to “1”, this bit enables the receiver line sta-
	tus interrupt.
Bit 1	THREIE (Transmitter Holding Register Empty Interrupt Enabled)–when set to “1”, this bit enables
	the Transmitter Holding register empty interrupt.
Bit 0	RDAIE (Received Data Available Interrupt Enabled)–when set to “1”Programmer’s Guide, this bit
	enables the received data available interrupt.

10.1.9 Transmitter Holding Register (THR)

Register 0

(DLAB = 0)

THR

The THR (Transmitter Holding register) is a write-only register used for sending data and AT commands to the modem.

10.1.10Receiver Buffer Register (RBR)

Register 0

(DLAB = 0)

RBR

The RBR (Receiver Buffer register) is a read-only register used for receiving data and AT command responses from the modem.

126 Intel Confidential Programmer’s Guide