HP 13255 Technical Information page 26

13?5-;
General Purpose asynChronous Data romm Module
13255-91089/24
AUG-01-76
4.1 CUSTOM BAllO Rl\TF. STRAPPING.
The custom baud rate generator provides a cloCk that is 16 times the
desired
b~ud
rate. The ranqe of baud rates is from
37.5
to 2400 baud
(within
1.0
percent). In addition,
ce~tain
rates from
2400
to 19.2K
baud are also provided.
The
~aud
rate switches arp confiqured as follows. (The example confiq-
uration is for tlO haud selection.)
a) Divide
153600
by the desired baud
rat~.
t~3600/110
=
1396.36
h) Round the quotient to the nearest integer.
1396.J6 becomes 1396
C)
Subtract one from the rounded
quoti~nt.
1396-1
=
1395
d) Convert the decimal number to a 12-bit binary number.
MSB LSB
SWITCH
Bl1 RIO S9 8A 87 86 85 64 83 82 81 BO
1395
o
1
o
o
1 1
o
1
e) Close a switch in every position that has a "1". The
remaininq switches are left onen.
f) To calculate the actual qenerated baud rate, divide
1~3600
by the result of step h, above.
1~36ry0/1396
=
110.03
(Note: The actual rate may not be exactly
equal to the desired rate.)
1
To.CIOCK the receive half of the UART with a
~ustom
baud rate,. the CSE
Switch must be.closed and bits, 1, 2, and 3 of the control reqister
must he "0" (F,xternal Clock).