Teletype 43 Teleprinter Basic RO, Service Manual

Page: 199 / 222

MEMORY AND DATA BUFFERS
There are two types of memory in the terminal -
nonvolatile and volatile. See the directory card for
a record of the total memory size provided.
The nonvolatile memory stores the user programmable
options that provide many of the operational charac­
teristics of your terminal. About
600 characters of
memory space are used for this purpose.
The volatile memory is divided into Send and Receive
data buffers. The size of the receive buffer is a user
programmable option (RBsze ). The remaining memory
space is the send buffer size ie, total memory, minus
600, minus (RBsze) =send buffer size.
Note: In order to copy the entire contents of the
send buffer locally (half-duplex operation), the receive
buffer size should typically be, at least equal to the
send buffer size.
Send Buffer
The send buffer is divided into three sections: Edit,
Data Stored But Not Sent and Data Already Sent.
Data is not treated
as
sent until the message is acknowl­
edged either by receiving a StrSn character
or depressing the ..
Send Buffer Organization
The Edit Buffer accepts data from the keyboard. The
edited data, when stored in the Data Stored But Not
Sent section, is the source of the send data. After
having been sent and acknowledged, messages remain
in the Data Already Sent section until the space is
needed for composing new messages or until inten­
tionally cleared by entering the Options Prep Mode.
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