Transmission Sequence - IBM 5280 Technical Newsletter

Page of SY31-0600-1
As updated April 15, 1981
By TN L SN20-9588
Transmission Sequence
As shown in the following illustration, the 16-bit frame
carries 12 bits of information:
Printer
Fill bits
(always 000)
Receive
Fill bits
(always 000)
Printer Attachment
I
' " ' '
' ; [ ' o E S v T e o n _ p ( l _ a l r i ~ t y )
_ _ _ ........ _ _ _ _ fParilV Bit for Even Parity
, L r i n t e r Address (000 through 110)
[
status _ _ _ _ _ ...,J['--S_ta_tus _ _ _
I
sync
_ _
. 4 . - _
r
Svnc
Bit
Bil
_
........
_-
9
10 11 12 13 14 15 3 4 5 6 9 10 11 12 13 14 15
~lo
_ _ _ _
o...,Jl,--p~I
______
l~l_x
_________________
x~I~II===~~10
_______
p~I_@
__ @ ___
@~I_x
_________________
x~l_l~I_00_Ol_ll_1~
________
~11
------------------------------------~------------------------------------------~----
-----------
Last Frame Additional
Frames
Printer Attachment
Transmit
Fill Bits (always 000) Fill Bits (always 000)
First Frame
Printer
Frame
Synchro-
Bit
Synchro-
nization nization
(6
half bits)
I
, , , ; , ,
'['oESTveon (P
1
a
1
ri
1
t)y IparilV Bit for Even Parity ,
L
Printer Address (000 through 110)
, , Lommand MOdi:ier L m m a n d Modifier
rCommand
01'
Data
~Command
or Data
_---'-__ _ _______
~L
_________
r:~tnc
_ - - ' - _ _ _ ________ .....
L _________
r
Sync
Bit
2 3 9 10 11 12 13 14 15 5 6 9 10 11 12 13 14 15
= 1
0=====0 =1 =p=I======1 :1 =x================x :1 :1
[=
=:1
0 0 0 P 1 @ @ @ l x x 1 1 1 000111 1
------------------~----------------------------------------~----------------~
----
-----------
Last Frame Additional
Frames
The fill bits, always 000, act as a timing delay. The parity
bit makes the number of active bits in the frame even.
The printer decodes the address bits (4 through 6) and
responds to the address by sending a response frame that
contains the address. Printer address bits of 111 indicate
a DSTD (data stream termination delimiter), which indi-
cates the end of the message and causes a line
turnaround~
A line turnaround extends from the time a printer receives
the last bit of a frame until the same printer starts sending
bit and frame synchronization bits. Bits 7 through 14 are
the data or command sent by the printer or the twinaxial
printer adapter Bit 15 (always 1) is the synchronization bit
for both the twinaxial printer adapter and the printer.
The transmission rate is 1.0 MHz (16 microseconds per
frame). The frame bit assignment during both transmit
and receive operations is shown in the previous illustration.
First Frame
Frame
Bit
Synchro-
Synchro-
nization nization
(6
half bits)
Twinaxial Printer Interface Commands
The following commands are generated by the twinaxial
'printer MPU and sent through the twinaxial printer adapter
to the printer in the command frame. These:commands are
not programmed by the user.
Activate-Read Command (00000000)
The activate-read command is inserted between a read
status command and the data frame that- follows it. The
activate-read command is issued when a not-busy,
no-exception, and no-line-parity response is returned
to a poll command following the read command.