ST16C552AIJ68 datasheet(6/39 Pages) EXAR

6 / 39 page

ST16C552/552A

Rev. 3.40

Symbol

Signal Type

Pin Description

reached.

SLCT

Select (with internal pull-up) - General purpose input or line

printer select status. Normally this pin is connected to a

printer output (active low) that indicates the ready status of

a printer, i.e., on-line and/or on-line and ready.

-SLCTIN

I/O

Select In (open drain, with internal pull-up) - General

purpose I/O or line printer select. This pin can be read via

Bit-3 in the printer command register, or written via bit-3 in

the printer control register. As this pin is open-drain, it can

be wire-or’d with other outputs. Normally this signal is

connected with a printer to select the printer with an active

low.

-STROBE

I/O

Strobe (open drain, with internal pull-up) - General purpose

I/O or data strobe output. Normally this output is connected

to a printer and indicates that valid data is available at the

printer port (PD0-PD7).

-TXRDY A/B

22,42

Transmit Ready A/B (active low). These outputs provide the

TX FIFO/THR status for individual transmit channels (A-B).

As such, an individual channel’s -TXRDY A-B buffer ready

status is indicated by logic 0, i.e., at least one location is

empty and available in the FIFO or THR. This pin goes to

a logic 1 when there are no more empty locations in the

FIFO or THR.

VCC

23,40,64

Pwr

2.97 to 5.5V power supply input. All inputs are 5V tolerant

except for XTAL1 and all printer port inputs for devices with

revision "F" and newer.

-CD A/B

29,8

Carrier Detect (active low) - These inputs are associated

with individual UART channels A through B. A logic 0 on this

pin indicates that a carrier has been detected by the modem

for that channel.

-CTS A/B

28,13

Clear to Send (active low) - These inputs are associated with

individual UART channels, A through B. A logic 0 on this pin(s)

indicates the modem or data set is ready to accept transmit

data from the 552/552A for the given channel. Status can be

tested by reading MSR bit-4 for that channel(s). -CTS has no

SYMBOL DESCRIPTION

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