Reset And Diagnostic Commands; Twinaxial Printer Attachment 16-Bit Frame Concept; Bi-Phase Encoding - IBM 5280 Technical Newsletter

Receive-Read Command
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This command loads the contents of the serdes (received
data) into the 100 register.
Reset and Diagnostic Commands
Reset Command
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To the twinaxial printer adapter, this command performs the
same function as power-on reset.
Diagnostic-Mode Command
This command starts a diagnostic test for the twinaxial
printer attachment. Data is not transmitted during this test.
The data from the output of the serdes is wrapped back to
the input of the serdes, where it is checked as during a
normal read operation. This checks the twinaxial printer
adapter transmit and receive circuitry for proper operation.
Diagnostic- Reset Command
This command is used with the diagnostic mode command.
It resets the serdes, but it leaves the twinaxial printer adapter
in transmit mode.
TWINAXIAL PRINTER ADDRESSING
The twinaxial printer attachment
MPU
selects a printer by
placing the printer address into the 10DB register. The'
following are the meanings of the 10DB register bits:
Bit(s) Meaning
0-2
3-4
Not used.
Port
addr~s
(used to select ports 20 through 23
for the four-port adapter; or port 20 for the
one-port adapter).
5-7 Printer address: These bits are loaded into the
serdes for each transmission. In receive mode,
these bits are compared with the address received
from the printer.
For a description of the printer addresses that can be
assigned to each port, see 705 in the maintenance
section.
Page of SY31-060o-1
As updated April 15, 1981
By TN L SN20-9588
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TWINAXIAL PRINTER ATTACHMENT 16-BIT FRAME
CONCEPT
Information between the printer and the twinaxial printer
adapter is transmitted by a 16-bit frame.
Bi-Phase Encoding
Each bit of the 16-bit frame to and from the printer is}
bi-phase encoded to ensure that a transition occurs during
each bit time (a 0 to a 1 transition for a 0 bit and a 1 to a
o
transition for a 1 bit). Because the transition divides
the bit into two parts, the term half bit is used in the
following description. No transition during a bit tir,ne is
called a
code violation.
When information is to be sent on the twinaxial cable, a
pattern of five 1-bits (1010101010 half bits) are sent to
establish bit synchronization. Immediately after the 1-bits,
the code violation (three half-bit 1's and three half-bit O's) is
sent to establish frame synchronization. After the frame
synchronization, the frame is sent starting with the sync
bit as shown in the following illustration:
1
Bit
-
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fl=
Logical 1 = 10
Jl
= Logical 0=01
n=ll'
U=OO
11 and 00 are valid
only during frame
synchronization.
111 000
'-_________
+------~
Sync Bit
Frame (bit 15 of
Bit Synchronization
(5 logical 1 's) Synchronization first frame)
Printer Attachment 271