Measurement-computing Micro 488/EX rev.2.1 Manual do Utilizador descarregar pdf (Página 44)

Section 4 General Programming

4.2

USER heap and issued without regard to controlling the receipt and

buffering of additional data.

When the serial input buffer requests one of the last 10 queues (1270

character locations left), it signals the serial host that it should stop sending

data. This is accomplished by either un-asserting the serial hardware

handshake

RTS

line or issuing an

XOFF

character (

&h13

), depending on

which serial handshake control has been switch selected. When more than

10 queues become available, it asserts

RTS

or issues an

XON

character

(

&h11

4.2.2 Log Buffer

The

LOG

buffer is similar to the serial output buffer. It can, under

program control, accept the data which would normally go to the serial

output buffer. It differs from the serial output buffer in that the data in the

LOG

buffer is maintained when the power is off. The

LOG

buffer is initially

allocated a 127 byte queue and, if required, acquires additional memory

from the USER heap. It retains these queues until

ERASE

d by the user

under program control.

4.2.3 Macro Buffers

MACRO

queues are not allocated until a macro is defined. If a

MACRO

ERASE

d, all the memory allocated to it is returned to the USER heap. The

MACRO

text is stored into this queue exactly the way it was received from

the serial input. Syntax error checking is not performed when the

MACRO

created. If the length of the

MACRO

is longer than the 127 bytes allocated,

additional memory is allocated as required in 127 byte lengths. A single

MACRO

could be defined to consume the entire available USER heap.

When a

MACRO

is executed, a copy of the

MACRO

buffer is made and

placed at the start of the serial input buffer. If there is no available memory

in the USER heap, an

OUT

MEMORY

error is generated which will cause

the front panel error LED to flash.

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