ST9 datasheet(34/146 Pages) STMICROELECTRONICS

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ST9 USER GUIDE

r5,#Num_loop

; number of elements to move

loop:

lddd

(rr2)+, (rr0)+

; transfer of one byte

djnz

r5,loop

The lddd instruction is coded using 2 bytes and executed in 14 cycles.

Here are the four possible data transfers:

These four instructions improve the performance of data block moves (frequently used in C

programs).

As you can see in the table above, the data move can be between data and program seg-

ments. Here’s an example of a data move from a Data segment using the DPR register to a

Program segment using the CSR register:

rr0,#Source

rr2,#Destination

; initialisation of the pointers

r5,#Num_loop

; number of elements to move

loop:

ldpd

(rr2)+, (rr0)+

; transfer of one byte

djnz

r5,loop

The data load with rr0 comes from the data segment selected by one of the four DPR register

values depending on the rr0 value and then are stored in the program segment selected by the

CSR register value.

(Please refer to the MMU Section 3.1.7 for an explanation of data and program segments).

3.3.1.2 Test Under Mask

These instructions, tm and tmw, perform a logical (bitwise) AND between the two operands,

but do not store the result. They only set the Z and S bits of the flag register for a later condi-

tional jump on zero or sign. The mask is a value in which the bits that are set to 1 select the

corresponding bits of the value to be tested for non-zero. As an example, in the following in-

struction:

tm value, mask

Instruction

Moves data from...

...to

lddd

data segment (uses the DPR0-DPR3 registers)

data segment

ldpp

program segment (uses the CSR register)

program segment

lddp

program segment

data segment

ldpd

data segment

program segment

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