ST16C552 Datasheet, PDF (4/39 Pages) Exar Corporation – DUAL UART WITH 16-BYTE FIFO AND PARALLEL PRINTER PORT

ST16C552/552A
SYMBOL DESCRIPTION
Symbol
-ERROR
GND
INIT
INT A/B
-INTP
INTSEL
Rev. 3.40
Pin
Signal Type
Pin Description
63
2,7,54
27
57
45,60
59
43
I
Error, Printer (with internal pull-up) - General purpose input
or line printer error. This pin may be connected to the active
low (logic 0) output of a printer to indicate an error condition.
Pwr
Signal and Power Ground.
I/O
Initialize (open drain, with internal pull-up) - General pur-
pose I/O signal. This pin may be connected for initialization
service of a connected line printer. Generally when this
signal is a logic 0, any connected printer will be initialized.
O
Interrupt output A/B ( three state active high) - These pins
provide individual channel interrupts, INT A-B. INT A-B are
enabled when MCR bit-3 is set to a logic 1, interrupts are
enabled in the interrupt enable register (IER), and when an
interrupt condition exists. Interrupt conditions include: re-
ceiver errors, available receiver buffer data, transmit buffer
empty, or when a modem status flag is detected.
O
Printer Interrupt, - This pin can be used to signal the
interrupt status of a connected printer. This pin basically
tracks the -ACK input pin, When INTSEL is a logic 0 and
interrupts are enabled by bit-4 in the control register. A
latched mode can be selected by setting INTSEL to a logic
1. In this case the interrupt -INTP is generated normally but
does not return to the inactive state until the trailing edge of
the read cycle (-IOR pin). -INTP is three stated until CON
bit-4 is set to a logic 1. The difference between the
ST16C552 and ST16C552A is the output state of INTP.
INTP is active high (logic 1) on the ST16C552 whereas
INTP is active low (logic 0) on the ST16C552A part when the
interrupt latch mode is selected.
I
Interrupt Select mode - This pin selects the interrupt type for
the printer port (-INTP). When this pin is a logic 0, the
external -ACK signal state is generally followed, minus
some minor propagation delay. Making this pin a logic 1 or
connecting it to VCC will set the interrupt latched mode. In this
case the printer interrupt (-INTP) will not return to a logic 0 on
the 552 or a logic 1 on the 552A (552A is inverted), until the
4