pTAL Conversion Guide

pTAL Built-In Routines

pTAL Conversion Guide—527302-002

18-36

$MOVEANDCXSUMBYTES

checksum input,output

uINT:variable

contains an initial value for the checksum. When $MOVEANDCXSUMBYTES

completes, checksum contains the newly computed checksum.

destaddr input,output

EXTADDR:variable

is the extended memory address to which $MOVEANDCXSUMBYTES moves

data. When $MOVEANDCXSUMBYTES completes, destaddr points to the

memory location following the last byte written.

srcaddr input,output

EXTADDR:variable

is the extended memory address from which bytes are read. When

$MOVEANDCXSUMBYTES completes, srcaddr points to the memory location

following the last byte read.

count input

uINT:value

is the number of bytes to move.

$MOVEANDCXSUMBYTES transfers count bytes from srcaddr to destaddr and

computes a checksum (bytewise exclusive “or”) on the data moved. When

$MOVEANDCXSUMBYTES completes, srcaddr points to the immediate right of the

last byte read, destaddr points to the immediate right of the last byte written, and

checksum holds the newly computed checksum.

$MOVEANDCXSUMBYTES does not ensure that the source and destination buffers

do not overlap.

Figure 18-14. TAL Code Equivalent to $MOVEANDCXSUMBYTES Routine

CODE(STRP 7);

STACK checksum, dest, source, count;

CODE(MBXX);

CODE(STRP 4);

STORE source, dest, checksum;