Analog Devices adsp-2100 Manual page 99

stored to the 8 lower bits of the memory word.
From the DMD bus, the PX register may be:
1. Loaded with a data move instruction, explicitly specifying the PX
register as the destination. The lower 8 bits of the data value are used
and the upper 8 are discarded.
PX = AX0;
2. Read with a data move instruction, explicitly specifying the PX register
as a source. The upper 8 bits of the value read from the register are all
zeroes.
AX0 = PX;
Whenever any register is written out to program memory, the source
register supplies the upper 16 bits. The contents of the PX register are
automatically added as the lower 8 bits. If these lower 8 bits of data to be
transferred to program memory (through the PMD bus) are important,
you should load the PX register from DMD bus before the program
memory write operation.
Data Transfer 4
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