Datasheet

TL16C451, TL16C452
ASYNCHRONOUS COMMUNICATIONS ELEMENTS
SLLS053C – MAY 1989 – REVISED AUGUST 1999
6
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
Terminal Functions (continued)
TERMINAL
I/O
DESCRIPTION
NAME
†
NO.
I/O
DESCRIPTION
PD0–PD7 53–46 I/O Parallel data bits (0–7). These eight lines provide a byte-wide input or output port to the system. The
eight lines are held in a high-impedance state when LPTOE
is high.
PE 67 I Printer paper empty. This is an input line from the printer that goes high when the printer runs out of
paper.
RESET
39 I
Reset. When active (low), RESET clears most ACE registers and sets the state of various output
signals. Refer to Table 2.
RI0
RI1 [GND]
30
6
I
Ring indicator. RIx is an active-low modem status signal. Its state can be checked by reading bit 6 (RI)
of the modem status register. Bit 2 (TERI) of the modem status register indicates that the RIx
input has
transitioned from a low to a high state since the last read from the modem status register. If the modem
status interrupt is enabled when this transition occurs, an interrupt is generated.
RLSD0
RLSD1 [GND]
29
8
I
Receive line signal detect. RLSDx is an active-low modem status signal. Its state can be checked by
reading bit 7 of the modem status register. Bit 3 (DRLSD) of the modem status register indicates that
this signal has changed states since the last read from the modem status register. If the modem status
interrupt is enabled when RLSDx
changes state, an interrupt is generated. This bit is low when a data
carrier is detected.
RTS0
RTS1 [NC]
24
12
O
Request to send. When active (low), RTSx informs the modem or data set that the ACE is ready to
transmit data. RTSx
is set to its active state by setting the RTS modem control register bit and is set
to its inactive (high) state either as a result of a reset or during loop mode operations or by clearing bit
1 (RTS) of the modem control register.
SIN0
SIN1 [GND]
41
62
I Serial input. SINx is a serial data input from a connected communications device.
SLCT 65 I Printer selected. SLCT is an input line from the printer that goes high when the printer has been selected.
SLIN
58 I/O
Printer select. SLIN is an open-drain line that selects the printer when it is active (low). An internal pullup
is provided on this line.
SOUT0
SOUT1 [NC]
26
10
I Serial output. SOUTx is a composite serial data output to a connected communication device. SOUTx
is set during a reset.
STB
55 I/O
Printer strobe. STB is an open-drain line that provides communication synchronization between the
TL16C451/TL16C452 and the printer. When it is active (low), it provides the printer with a signal to latch
the data currently on the parallel port. An internal pullup is provided on this line.
V
CC
23,40,
64
5-V supply voltage
GND 2,7,9
22,27,42,
43,54,61
Supply common
†
Names shown in brackets are for the TL16C451.