IBM 2790, Руководство пользователя, Страница: 42 / 88

A System/360 to 2715 transaction may contain up to 126
bytes, including an eight-byte header that must be provided
by the System/360 problem program. The transaction head­
er contains the following information:
1 st byte Length (binary)
2nd byte Control (binary)
3rd byte Area station address (binary)
4th byte Device address (binary)
5th-8th byte Time stamp (EBCDIC)
Length. A binary count of the number of bytes in the
transaction including the eight-byte header. The maximum-
length transaction is 255 bytes from 2715 to System/360 or
126 bytes from System/360 to 2715. Output transactions
will normally be formatted as a line of print.
Control. A binary code that specifies the type of transaction.
Figure 24 shows a list of assigned transaction controls.
Area Station Address. A binary address byte specifying
which one of
100
area stations in the system is either the
data source or data recipient. Valid addresses are hexadeci­
mal 80 through E3 for area station transactions, or 00 for
non-area station transactions.
Device Address. A binary address byte which specifies one
of 32 data entry units; a 1053 Printer; a 1035 Badge Reader;
a digital device input (OEM); or a 2791 resident card reader,
badge reader, or manual entry unit. The device addresses
(hexadecimal) are:
Badge R e a d e r......................... X‘80’ (80 hex)
Card R e a d e r ..........................X‘84’
Keyboard (manual entry) . . X‘
8 8
’
Digital Device Read-In . . . X‘
8
C’
1035 Badge Reader . . . . X‘81’- ‘83’
1053 P r i n t e r ..........................X‘40’
Data Entry U n its .................... X‘C0’- ‘DF’
Time Stamp. A four-byte field which contains the value of
the clock when the transaction was received. It is carried in
24-hour form, in hours and minutes, as EBCDIC characters.
For System/360 to 2715 messages, this field is optional; if
not used for time, it must contain valid EBCDIC numeric
characters.
The Message
All messages are composed of one message header, one or
more transaction headers with the corresponding text, and
the BSC framing control characters. Message formatting is
completely flexible within the limits of message and trans­
action definitions.
2715 to System/360 Message. The 2715 to System/360
| message length is limited to a maximum of 612 bytes—mes­
sage header, 5 bytes; transaction header(s),
8
bytes; and
text. The message-header format is defined as follows:
First, Second, and Third Byte—Day Number (EBCDIC)
Fourth and Fifth Byte—Restart Number (bit-significant
and binary)
Day Number. A three-byte EBCDIC field which contains
a customer-specified day number.
Restart Number. A two-byte field which defines type of
data and associated restart information. Bit 9 indicates
this message is deferred data; bit
10
indicates this mes­
sage is priority data; the remaining bits indicate a disk
address.
System/360 to 2715 Message. The System/360 to 2715
message length is limited to 128 bytes—message header,
2
bytes; transaction header(s),
8
bytes; and text. The message
header format is defined as follows:
First Byte—Length (binary)
Second byte—Control (bit-significant)
Length. A binary count of the number of bytes in the
message, including the message header. The BSC framing
control characters are not included in the count.
Control A bit-significant byte which indicates one of
three destinations for output data. The following hexa­
decimal notation indicates output destination:
X‘01’ — 1053 Printers
X‘02’ — 2715 Control Message
X‘04’ - 2740 Terminal
Messages originating at the System/360 to be printed on
the 2740 attached to the 2715 TCU or to be printed on the
1053 attached to an area station must have the format
shown in Figure 25.
The 2715 will accept multiple messages within the limita­
tions of the 2715 core-storage sizes:
2715-16K B ytes. The 2715 will accept consecutive mes-
1 sages for a maximum of 630 internally allocated bytes
before forcing System/360 to “wait before transmitting”
(WACK). As the byte count decreases to 504 bytes or
less, the 2715 will accept one or more subsequent
messages.
2715-32K Bytes. The 2715 will accept consecutive
I messages for a maximum of 1260 internally allocated
bytes before forcing System/360 to “wait before trans­
mitting” (WACK). As the byte count decreases to 1134
bytes or less, the 2715 will accept one or more subsequent
messages.
Internally Allocated Bytes. Due to internal control require­
ments, the following table should be used to determine the
number of bytes required by the 2715 to buffer a
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