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ST7 AND ST9 PERFORMANCE BENCHMARKING

8.9 16-BIT VALUE RIGHT SHIFT

8.10 BIT MANIPULATION

8.11 TIMER INTERRUPT

Algorithm

The 16-bit value right shift routine shifts a 16-bit value five places to the right.

Implementation

The operand to be shifted is 40h (hexadecimal value). It is taken into account as a 16-bit integer

and it is the 16-bit value which is shifted.

Features stressed

It is a test measuring the word (16-bit) and bit manipulation capability.

Algorithm

The Bit manipulation benchmark performs the set, the reset, and the test of 3 bits in a 128-bit

array.

Implementation

The memory where some bits will be set, reset, and tested, is initialized with the 'Ah' value

(hexadecimal value). It is composed of 8 words '0AAAAh', which represents a 16-byte memory

area, that is to say a 128-bit array.

The test consists in setting, resetting, and then testing the 10th bit of the array, then the 13th bit

of the array, and then the 123rd bit of the array. Setting a bit is setting it to 1. Resetting a bit is

resetting it to 0. And testing a bit is testing it and setting it to 1 if zero (with the zero flag Z also

set if zero).

Features stressed

This benchmark measures the computational capability and the efficiency in bit

manipulation.

Algorithm

The Timer interrupt benchmark is composed of two routines performing an input capture interrupt

and an input capture/output compare interrupt.

Implementation

The first routine is the body of an interrupt service routine handling a timer input capture.

The second is the body of an interrupt service routine handling a timer input capture or a output

compare; as interrupt vectors can be separate, this routine may be composed of two different

parts.

The routines include:

• the average instruction (that is an instruction lasting the average instruction cycle time)

which is interrupted and the interrupt entry process (they represent the interrupt latency)

• the body of a typical interrupt service routine including the following operations:

- stack two registers or change register bank (if not done by interrupt processing)

- read timer register

- call to a subroutine with input capture register content as input parameter or output

compare register content as output parameter

- return from subroutine

- unstack registers or restore register bank (if not done by interrupt processing)

- return from interrupt

It is true that each MCU has its specific own manner of handling interrupts. Reading the timer

judged as a satisfying way to do so. Thus, it has been chosen as routine body.

Features stressed

This benchmark measures the interrupt processing performance.

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