RDLONG
Instruction: Read long of main memory.
RDLONG Value, < # > Address
Result: Long is stored in Value.
- Value (d-field) is the register to store the long value into.
- Address (s-field) is a register or a 9-bit literal whose value is the main memory address to read from.
Opcode Table:
–INSTR– ZCRI –CON– –DEST– –SRC– | Z Result | C Result | Result | Clocks |
000010 001i 1111 ddddddddd sssssssss | Result = 0 | — | Written | 8..23 |
Concise Truth Table:
In | Out | ||||||
Destination | Source | Z | C | Effects | Destination1 | Z2 | C |
$----_----; - | $----_----; - | - | - | wz wc | long value | 0 | 0 |
1 Destination Out is always generated since including an NR effect would turn RDLONG into a WRLONG instruction.
2 The Z flag is cleared (0) unless Destination Out equals 0.
Explanation
RDLONG syncs to the Hub, reads the long of main memory at Address, and stores it into the Value register. Address can point to any byte within the desired long; the address' lower two bits will be cleared to zero resulting in an address pointing to a long boundary.
If the WZ effect is specified, the Z flag will be set (1) if the value read from main memory is zero. The NR effect can not be used with RDLONG as that would change it to a WRLONG instruction.
RDLONG is a hub instruction. Hub instructions require 8 to 23 clock cycles to execute depending on the relation between the cog's hub access window and the instruction's moment of execution. See Hub for more information.
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