TL16C554, TL16C554I

ASYNCHRONOUS COMMUNICATIONS ELEMENT

SLLS165D – JANUARY 1994 – REVISED JULY 1998

5

POST OFFICE BOX 655303

Terminal Functions (Continued)

TERMINAL

NAME

FN

NO.

PN

NO.

I/O

DESCRIPTION

INTA, INTB,

INTC, INTD

15, 21,

49, 55

27, 34,

67, 74

O

External interrupt output. The INTx outputs go high (when enabled by the interrupt register) and

inform the CPU that the ACE has an interrupt to be serviced. Four conditions that cause an interrupt

to be issued are: a receiver error, receiver data available or timeout (FIFO mode only), transmitter

holding register empty, and an enabled modem status interrupt. The interrupt is disabled when it is

serviced or as the result of a master reset.

IOR

52

70

I

Read strobe. A low level on IOR transfers the contents of the TL16C554 data bus to the external CPU

bus.

IOW

18

31

I

Write strobe. IOW allows the CPU to write into the selected address by the address register.

RESET

37

53

I

Master reset. When active, RESET clears most ACE registers and sets the state of various signals.

The transmitter output and the receiver input is disabled during reset time.

RIA, RIB,

RIC, RID

8, 28,

42, 62

18, 43,

58, 3

I

Ring detect indicator. A low on RIx indicates the modem has received a ring signal from the telephone

line. The condition of this signal can be checked by reading bit 6 of the modem status register.

RTSA, RTSB,

RTSC, RTSD

14, 22,

48, 56

26, 35,

66, 75

O

Request to send. When active, RTSx informs the modem or data set that the ACE is ready to receive

data. Writing a 1 in the modem control register sets this bit to a low state. After reset, this terminal

is set high. These terminals have no affect on the transmit or receive operation.

RXA, RXB

RXC, RXD

7, 29,

41, 63

17, 44,

57, 4

I

Serial input. RXx is a serial data input from a connected communications device. During loopback

mode, the RXx input is disabled from external connection and connected to the TXx output internally.

RXRDY

38

54

O

Receive ready. RXRDY goes low when the receive FIFO is full. It can be used as a single transfer

or multitransfer.

TXA, TXB

TXC, TXD

17, 19,

51, 53

29, 32,

69, 72

O

Transmit outputs. TXx is a composite serial data output that is connected to a communications

device. TXA, TXB, TXC, and TXD are set to the marking (high) state as a result of reset.

TXRDY

39

55

O

Transmit ready. TXRDY goes low when the transmit FIFO is full. It can be used as a single transfer

or multitransfer function.

VCC

13, 30,

47, 64

5, 25,

45, 65

Power supply

XTAL1

35

50

I

Crystal input 1 or external clock input. A crystal can be connected to XTAL1 and XTAL2 to utilize the

internal oscillator circuit. An external clock can be connected to drive the internal clock circuits.

XTAL2

36

51

O

Crystal output 2 or buffered clock output (see XTAL1).

– 0.5 V to 7 V

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

– 0.5 V to 7 V

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Continuous total power dissipation at (or below) 70

°C

500 mW

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

– 0

°C to 70°C

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TL16C554I

–40

°C to 85°C

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

–65

°C to 150°C

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

† Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and

functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not

implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

NOTE 1: All voltage levels are with respect to GND.