Propeller Manual

WRBYTE – Assembly Language Reference
WRBYTE
Instruction: Write a byte to main memory.
WRBYTE Value, 〈#〉 Address
• Value (d-field) is the register containing the 8-bit value to write to main memory.
•
Address (s-field) is a register or a 9-bit literal whose value is the main memory
address to write to.
Opcode Table:
–INSTR– ZCRI –CON– –DEST– –SRC– Z Result C Result Result Clocks
000000 000i 1111 ddddddddd sssssssss
--- --- Not Written 7..22
Concise Truth Table:
In Out
Destination Source Z C Effects Destination
1
Z
2
C
$----_----; - $----_----; - - -
wz wc
n/a 1 0
1
Destination Out doesn’t exist since including a WR effect would turn WRBYTE into a RDBYTE instruction.
2
The Z flag is set (1) unless the main memory address is on a long boundary.
Explanation
WRBYTE synchronizes to the Hub and writes the lowest byte in Value to main memory at
Address.
The
WR effect can not be used with WRBYTE as that would change it to a RDBYTE instruction.
WRBYTE is a hub instruction. Hub instructions require 7 to 22 clock cycles to execute
depending on the relation between the cog’s hub access window and the instruction’s moment
of execution. See Hub on page 24 for more information.
Page 374 · Propeller Manual v1.1