80333 datasheet(27/75 Pages) INTEL

27 / 75 page

80333

Datasheet

Intel® 80333 I/O Processor Datasheet

May 2005

Order Number: 305433, Revision: 002

GPIO[4]/

U1_RXD

1I/O

General Purpose I/O: These pins may be selected on a per pin

basis as general purpose inputs or outputs. The default mode is a

general purpose input.

Serial Input: Serial data input from device pin to receive shift register.

GPIO[5]/

U1_TXD

1I/O

General Purpose I/O: These pins may be selected on a per pin

basis as general purpose inputs or outputs. The default mode is a

general purpose input.

Serial Output: Composite serial data output to the communications

link-peripheral, modem, or data set. The TXD signal is set to the

MARKING (logic 1) state upon a Reset operation.

GPIO[6]/

U1_CTS#

1I/O

General Purpose I/O: These pins may be selected on a per pin

basis as general purpose inputs or outputs. The default mode is a

general purpose input.

Clear To Send: When low, this pin indicates that the receiving UART

is ready to receive data. When the receiving UART deasserts CTS#

high, the transmitting UART should stop transmission to prevent

overflow of the receiving UARTs buffer. The CTS# signal is a modem-

status input whose condition may be tested by the host processor or

by the UART when in Autoflow Mode as described below:

Non-Autoflow Mode:

When not in Autoflow Mode, bit 4 (CTS) of the Modem Status

of the CTS# signal. Bit 0 (DCTS) of the Modem Status register

indicates whether the CTS# input has changed state since the

previous reading of the Modem Status register. CTS# has no effect

on the transmitter. The user may program the UART to interrupt the

processor when DCTS changes state. The programmer may then

stall the outgoing data stream by starving the transmit FIFO or

disabling the UART with the IER register.

Note:

When UART transmission is stalled by disabling the UART,

the user may not receive an MSR interrupt when CTS#

reasserts. This occurs because disabling the UART also

disables interrupts. As a workaround, the user may use

Auto CTS in Autoflow Mode, or program the CTS# pin to

interrupt.

Autoflow Mode:

Note:

In Autoflow Mode, the UART Transmit circuitry will check

the state of CTS# before transmitting each byte. When

CTS# is high, no data is transmitted.

GPIO[7]/

U1_RTS#

1I/O

General Purpose I/O: These pins may be selected on a per pin

basis as general purpose inputs or outputs. The default mode is a

general purpose input.

Request To Send: When low, this informs the remote device that

the UART is ready to receive data. A reset operation sets this signal

to its Inactive (high) state. LOOP mode operation holds this signal in

its Inactive state.

Non-Autoflow Mode:

The RTS# output signal may be asserted by setting bit 1 (RTS) of

the Modem Control register to a 1. The RTS bit is the complement

of the RTS# signal.

Autoflow Mode:

RTS# is automatically asserted by the Autoflow circuitry when the

Receive buffer exceeds its programmed threshold. It is deasserted

when enough bytes are removed from the buffer to lower the data

level back to the threshold.

Total

Table 12.

UART Signals (Sheet 2 of 2)

Name

Count

Type

Description

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