122-32000 Parallax Inc, 122-32000 Datasheet - Page 368

• Manufacturer Part Number: 122-32000
• Description: MANUAL PROPELLER
• Manufacturer: Parallax Inc

Specifications of 122-32000

• Accessory Type: Manual
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: Propeller Education (PE) Kit
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Conditions
Every Propeller Assembly instruction has an optional “condition” field that is used to
dynamically determine whether or not it executes when it is reached at run time. The basic
syntax for Propeller Assembly instructions is:
〈
The optional Condition field can contain one of 32 conditions (see Table 5-2) and defaults to
IF_ALWAYS
value used for the
This feature, along with proper use of instructions’ optional Effects field, makes Propeller
Assembly very powerful.
conditionally executed based on the results. Here’s an example:
The first instruction,
the C flag because the
that could affect the C flag, but they do not affect it because no
means that the state of the C flag is preserved since it was last modified by the first
instruction. The last four instructions are conditionally executed based on the state of the C
flag that was set five instructions prior. Among the last for instructions, the first two
instructions have
last two
In this case, the two pairs of
When an instruction’s condition evaluates to
NOP
code such as this example very deterministically timed.
Page 368 · Propeller Manual v1.0
Label
, elapsing 4 clock cycles but affecting no flags or registers. This makes multi-decision
〉 〈
mov
Condition
if_nc
if_nc
if_c
if_c
when no condition is specified. The 4-bit
instructions have
〉
(
if_nc
–CON–
Instruction
IF_x
test
and
shl
shr
movd
mov
mov
mov
mov
test _pins, #$20
WC
conditions, causing them to execute only “if not C” (if C = 0). The
field in the instruction’s opcode.
effect was specified. The next four instructions perform operations
mov
)
Flags can be affected at will and later instructions can be
〈
if_c
Effects
_pins, #$20
_pins, #$38
t1, _pins
_pins, #3
vcfg, _pins
dira, t1
dirb, #0
dira, #0
dirb, t1
instructions are executed in a mutually-exclusive fashion.
conditions, causing them to execute only “if C” (if C = 1).
〉
wc
, performs its operation and adjusts the state of
FALSE
, the instruction dynamically becomes a
wc
Value
shown for each condition is the
WC
effect was specified. This
mov