PC16552D datasheet(13/24 Pages) TI1

13 / 24 page

60 Pin Descriptions (Continued)

RI1 RI2

(Ring Indicator) pins 43 31 When low this indi-

cates that a telephone ringing signal has been received by

the MODEM or data set The RI signal is a MODEM status

input whose condition the CPU can test by reading bit 6 (RI)

of the MODEM Status Register for the appropriate channel

Bit 6 is the complement of the RI signal Bit 2 (TERI) of the

MODEM Status Register indicates whether the RI input sig-

nal

has changed from a low to a high state since the previ-

ous reading of the MODEM Status Register

Note

Whenever the RI bit of the MODEM Status Register changes from a

high to a low state an interrupt is generated if the MODEM Status

Interrupt is enabled

SIN1 SIN2

(Serial Input) pins 39 25 Serial data input from

the communications link (peripheral device MODEM or

data set)

SOUT1 SOUT2

(Serial Output) pins 38 26 Composite se-

rial data output to the communications link (peripheral

MODEM or data set) The SOUT signal is set to the Marking

(logic 1) state upon a Master Reset operation

TXRDY1 TXRDY2

(Transmitter Ready) pins 1 32 Trans-

mitter DMA signalling is available through two pins When

operating in the FIFO mode the CPU selects one of

two types of DMA transfer via FCR3 When operating as in

the 16450 Mode only DMA mode 0 is allowed Mode 0

supports single transfer DMA where a transfer is made be-

tween CPU bus cycles Mode 1 supports multi-transfer DMA

where multiple transfers are made continuously until the

XMIT FIFO has been filled Details regarding the active and

inactive states of this signal are given in Section 85 Bit 3

VDD (Power) pins 33 44 a5V Supply

VSS (Ground) pins 12 22 0V Reference

(Write) pin 20 When WR is low while the chip is select-

ed the CPU can write control words or data into the select-

ed DUART register

XIN

(External Crystal Input) pin 11 This signal input is used

in conjunction with XOUT to form a feedback circuit for the

baud rate generator’s oscillator If a clock signal will be gen-

erated off-chip then it should drive the baud rate generator

through this pin

XOUT

(External Crystal Output) pin 13 This signal output is

used in conjunction with XIN to form a feedback circuit for

the baud rate generator’s oscillator If the clock signal will

be generated off-chip then this pin is unused

70 Connection Diagram

Chip Carrier Package

TLC9426 – 17

Top View

Order Number PC16552D

See NS Package Number V44A

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