4
Pin Description
PIN TYPE SYMBOL DESCRIPTION
1V
CC
† Positive Voltage Supply
2 NC No Connection
3 GND Ground
4 I RRD A high level on RECEIVER REGISTER DISABLE
forces the receiver holding out-puts RBR1-RBR8
to high impedance state.
5 O RBR8 The contents of the RECEIVER BUFFER REGIS-
TER appear on these three-state outputs. Word for-
mats less than 8 characters are right justified to
RBR1.
6 O RBR7 See Pin 5-RBR8
7 O RBR6 See Pin 5-RBR8
8 O RBR5 See Pin 5-RBR8
9 O RBR4 See Pin 5-RBR8
10 O RBR3 See Pin 5-RBR8
11 O RBR2 See Pin 5-RBR8
12 O RBR1 See Pin 5-RBR8
13 O PE A high level on PARITY ERROR indicates received
parity does not match parity programmed by control
bits. When parity is inhibited this output is low.
14 O FE A high level on FRAMING ERROR indicates the
first stop bit was invalid.
15 O OE A high level on OVERRUN ERROR indicates the
data received flag was not cleared before the last
character was transferred to the receiver buffer
register.
16 I SFD A high level on STATUS FLAGS DISABLE forces
the outputs PE, FE, OE, DR, TBRE to a high im-
pedance state.
17 I RRC The Receiver register clock is 16X the receiver
data rate.
18 I DRR A low level on DATA RECEIVED RESET clears
the data received output DR to a low level.
19 O DR A high level on DATA RECEIVED indicates a
character has been received and transferred to
the receiver buffer register.
20 I RRI Serial data on RECEIVER REGISTER INPUT is
clocked into the receiver register.
21 I MR A high level on MASTER RESET clears PE, FE,
OE and DR to a low level and sets the transmitter
register empty (TRE) to a high level 18 clock cycles
after MR falling edge. MR does not clear the receiv-
er buffer register. This input must be pulsed at least
once after power up. The HD-6402 must be master
reset after power up. The reset pulse should meet
V
IH
and t
MR
. Wait 18 clock cycles after the falling
edge of MR before beginning operation.
22 O TBRE A high level on TRANSMITTER BUFFER REGIS-
TER EMPTY indicates the transmitter buffer register
has transferred its data to the transmitter register
and is ready for new data.
23 I TBRL A low level on TRANSMITTER BUFFER REGIS-
TER LOAD transfers data from inputs TBR1-
TBR8 into the transmitter buffer register. A low to
high transition on TBRL initiates data transfer to
the transmitter register. If busy, transfer is auto-
matically delayed so that the two characters are
transmitted end to end.
24 O TRE A high level on TRANSMITTER REGISTER EMP-
TY indicates completed transmission of a charac-
ter including stop bits.
25 O TRO Character data, start data and stop bits appear se-
rially at the TRANSMITTER REGISTER OUTPUT.
26 I TRB1 Character data is loaded into the TRANSMITTER
BUFFER REGISTER via inputs TBR1-TBR8. For
character formats less than 8 bits the TBR8, 7 and
6 inputs are ignored corresponding to their pro-
grammed word length.
27 I TBR2 See Pin 26-TBR1.
28 I TBR3 See Pin 26-TBR1.
29 I TBR4 See Pin 26-TBR1.
30 I TBR5 See Pin 26-TBR1.
31 I TBR6 See Pin 26-TBR1.
32 I TBR7 See Pin 26-TBR1.
33 I TBR8 See Pin 26-TBR1.
34 I CRL A high level on CONTROL REGISTER LOAD
loads the control register with the control word. The
control word is latched on the falling edge of CRL.
CRL may be tied high.
35 I PI A high level on PARITY INHIBIT inhibits parity gen-
eration, parity checking and forces PE output low.
36 I SBS A high level on STOP BIT SELECT selects 1.5
stop bits for 5 character format and 2 stop bits for
other lengths.
37 I CLS2 These inputs program the CHARACTER
LENGTH SELECTED (CLS1 low CLS2 low 5 bits)
(CLS1 high CLS2 low 6 bits) (CLS1 low CLS2
high 7 bits) (CLS1 high CLS2 high 8 bits.)
38 I CLS1 See Pin 37-CLS2.
39 I EPE When PI is low, a high level on EVEN PARITY
ENABLE generates and checks even parity. A low
level selects odd parity.
40 I TRC The TRANSMITTER REGISTER CLOCK is 16X
the transmit data rate.
† A 0.1F decoupling capacitor from the V
CC
pin to the GND is
recommended.
PIN TYPE SYMBOL DESCRIPTION
HD-6402HD-6402
