HP 13255 Technical Information page 17

13255
General Purpose Asynchronous Data Comm Module
13255-91089/15
~ev
AUG-Ot-76
3.0 FUNCTIONAL PESCRIPTION. Pefer to .the block diagram (fiQure_1),
schematic d~aqra~.(figure 2), component location dl~qram (figure 3),
current loop confiqurations (figure 4), and parts lIsts
(02640-60089,
02640-60097, 02640-60098, 02640-60099,
and
02645-60003)
located in the
aOPE'ndix.
3.1
3.t.l
3.1.?
3.2
3.2.1
The functional
~escription
Of this module is detailed in blocks as
shown on the block
dia~ram.
UART. The UART is an MOS/LSI device used for interfacing a serial
asynchronous data path to a parallel data path. The baud rate, number
of stop bits, and parity configuratIon
Of
the received and transm1tted
serial
char~cters
can be
~roqrammed.
(For detaIls of the UART, consult
western DiqitAI's
TR16028
specifIcation sheet.)
Trans~itted
and received characters can have 6, 7, or 8 data bits
(excludlnQ parirv). All characters have one start bit.
Ch~racters
have one stop bit unless
110
baud Is selected or the 2SB Switch is
closed, in which case two stop bits are
use~.
5ii or seven-bit data
words can have even or odd
~arity.
Eight-bit data words have no
paritv.
When the
134
Switch is closed and control register bits 3, 2, and 1 are
"010", then 134.5 baud, six data ~its, one start bit, and one stop bit
are selected.
1/0
INSTRUCTION Of CODER.
The
1/0
l~struction
decoder is a circuit
whlc~
decodes terminal data
bus sjonals into hardware control signals on the
peA.
Tt
consist~
of
a module ad~ress decoder (U46) Rnd a 3-to-8 decoder (045). The module
address dpcoder is
co~pos~d
of four exclusive
OR
oates which can be
proorammed with switches. When the prooer module address Is oresent on
ADDR11,
ADOPIO,
ADOP9,
and
AOnR4,
an enable
si~nal
1.s provided to the
3-to-R decoder.