Propeller Manual

OUTA, OUTB – Assembly Language Reference
OUTA, OUTB
Register: Output registers for 32-bit ports A and B.
DAT
〈Label〉 〈Condition〉 Instruction OUTA, SrcOperand 〈Effects〉
DAT
〈Label〉 〈Condition〉 Instruction DestOperand, OUTA 〈Effects〉
DAT
〈Label〉 〈Condition〉 Instruction OUTB, SrcOperand 〈Effects〉 (Reserved for future use)
DAT
〈Label〉 〈Condition〉 Instruction DestOperand, OUTB 〈Effects〉 (Reserved for future use)
Result: Optionally, the output register is updated.
•
Label is an optional statement label. See Common Syntax Elements, page 250.
•
Condition is an optional execution condition. See Common Syntax Elements, page 250.
•
Instruction is the desired assembly instruction. OUTA or OUTB may be used in either the
assembly instruction’s DestOperand
or SrcOperand fields.
•
SrcOperand is a constant expression used by Instruction to operate on, and optionally
write to, the
OUTA or OUTB register in DestOperand.
•
DestOperand is a constant expression indicating the register that is operated on, and
optionally written to, using the value of
OUTA or OUTB in SrcOperand.
Explanation
OUTA and OUTB are one of six special purpose registers (DIRA, DIRB, INA, INB, OUTA and OUTB)
that directly affect the I/O pins. The
OUTA and OUTB register’s bits indicate the output states of
each of the 32 I/O pins in Port A and Port B, respectively.
OUTB is reserved for future use; the
Propeller P8X32A does not include Port B I/O pins so only
OUTA is discussed below.
OUTA is a read/write register usable in an instruction’s DestOperand or SrcOperand fields. If the
I/O pin is set to output, a low (0) bit in
OUTA causes it to output ground, and a high (1) bit causes
it to output VDD (3.3 volts). The following code sets I/O pins P0 through P3 to output high.
mov dira, #$0F
mov outa, #$0F
See Registers, page 338, and the Spin language OUTA, OUTB section, page 175, for more
information. Keep in mind that in Propeller Assembly, unlike in Spin, all 32 bits of
OUTA are
accessed at once unless the
MUXx instructions are used.
Page 330 · Propeller Manual v1.1