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The 2715 is a buffered core storage, microcoded control
unit, providing the user with a flexible central controller to
which Area Stations, Data Entry Units and other 1/0 devices
are attached. For purposes of this section, the user is as-
sumed to be controlling the system at the System/360
and the operator is operating and monitoring the system at
the Area Stations and Data Entry Unit locations.
The 2790 provides the user with a flexible communication
and information system. To achieve this, the user provides
a set of statements describing the processing that his input
must undergo. Since the 2715 is a hardware and microcode
type controller, it does not allow for complete user coding
control. Instead, the microcode interprets control require-
ments by means of a set of user-specified tables. These
tables contain pointers and index values as well as parameters
for the microcode.
The data link between the System/360 and the 2715 is
through the Binary Synchronous Communications (BSC)
interface, whether attachment is local or remote. Remote
attachment line speed permits a maximum data rate of 600
characters per second; local attachment permits approxi-
mately 3000 characters per second. The maximum-size
message that can be transmitted from the 2715 to Sys-
tem/360 is 640 bytes, excluding BSC framing control
characters. All messages are transmitted in EBCDIC trans-
parent code.
SYSTEM OPERATION
Data transactions, which originate on one of the devices
attached to the 2715, are formatted into messages and
either transmitted to the integral disk unit in the 2715 for
later retrieval by the user's BTAM program or are sent
directly to the System/360 without any intervening delays.
Messages from System/360 are sent to the 2715, which
acts on them immediately. These messages may be directed
to output devices attached to the 2715, or they may be
control-type messages that call upon the 2715 to modify
its opera ton in some way. If either the 2715 or the Sys-
tem/ 360 is incapable of receiving data for a temporary
period, normal BSC control sequences indicate this, and
the sender must wait. Should the data link be disabled for
some reason, the 2715 will enqueue all messages received
for later transmittal.
Transactions may be blocked together to make one
longer message, or be sent singly. This function is performed
automatically by the 2715 microcode on 2715 to Sys-
tem/360 messages, and performed by the user's problem
program on System/360 to 2715 messages.
Programming Considerations
OS and DOS Support
Telecommunications support under both OS/360 BT AM
and DOS/360 BTAM is being expanded to include support
for the 2715 Transmission Control Unit.
This support consists of modifications to BT AM and
new Assembler Macro definitions to support generation
of user table-defining statements to object format. For
detailed programming information, see IBM System/360
OS/DOS BTAM Planning for IBM 2790 Data Communica-
tion System Support, Form C30-1004.
BTAM Modifications
Two main modifications will be made to BT AM. One pro-
vides for centralized logging of errors collected by the 2715
relating to devices attached to it. This facility is useful for
Customer Engineering maintenance of the 2715 complex.
The second provides for 2715-originated messages to be
printed on the System/360 console. This means that the
System/360 operator can receive operator-awareness type
messages if the 2715 has no 2740 attached or if the 2740
requires intervention.
2715 User Table Assembly
Seven DOS/360 and OS/360 Assembler Language macros
define user tables for the 2715. The user tables define the
hardware configuration, the step-by-step terminal functions,
and the related 2715 functions.
CONFIGUR. The CONFIGUR macro is used to generate the
table definition block, which contains pointers to the 2715
tables.
AS. The AS macro is used to build an entry in the Area
Station table and the Data Entry Unit table, and a corres-
ponding entry in the Data Entry Unit index table.
TGROUP. The TGROUP (transaction group) macro is used
to define entries in a TGROUP table. Each keyword operand
associates a transaction list with a transaction code. A maxi-
mum of 63 TGROUP mac.ros are allowed.
TRLIST. The TRUST (transaction list) macro is used with
the Area Station list (ASLIST) macro and the Data Entry
Unit list (DEULIST) macro to define a transaction. When
the transaction is initiated by an Area Station, the TRUST
macro is followed by one or more ASLIST macros. When
the transaction is initiated by a Data Entry Unit, the TRUST
macro is followed by one or more DEUUST macros. The
first transaction list must be for all of the IBM 1035 Badge
Programming Considerations
57
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