The symbol for Rosetta Stone in the NYSE is: RST.
Because that's how Intel designed the 8085. In addition to the 8080 type interrupt on the INTR pin, Intel chose, for the 8085, to implement four new interrupts, RST 5.5, RST 6.5, RST 7.5, and TRAP, each of which would not require the interrupting device to provide a vector. The naming convention of x.5 was simply in recognition that Intel placed the implicit vector halfway between two other RST vectors. As an example, RST 6.5 is halfway between RST 6 and RST 7. Since RST 6 and RST 5 are eight bytes away from each other, placing RST 6.5 in between would place a limit of four bytes, and four bytes is enough to place a three byte JMP instruction. The decimal and hex addresses of all of the vectors are... RST 0 - 0 - 00H RST 1 - 8 - 08H RST 2 - 16 - 10H RST 3 - 24 - 18H RST 4 - 32 - 20H TRAP - 36 - 24H RST 5 - 40 - 28H RST 5.5 - 44 - 2CH RST 6 - 48 - 30H RST 6.5 - 52 - 34H RST 7 - 56 - 38H RST 7.5 - 60 - 3CH
The 5.5 in RST 5.5 means that the interrupt vector is located between RST 5 and RST 6.
RST OF TRAP is 24h(hexadecimail) address.
Because this mnemonic stands for RESTART (RST).
It is angle RST.
Rosetta Stone (RST)had its IPO in 2009.
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The 8085 has five interrupts, INTR, RST5.5, RST6.5, RST7.5, and TRAP. It also has eight software interrupts, RST0, RST1, ..., RST7. The INTR interrupt requires a hardware response that is an opcode. Usually, the opcode is either a CALL instruction, in which case the interrupt vector can go anywhere in memory, or it is an RST instruction, in which case the vector is based on a table in low memory. In the case of RST instructions, either directly or via INTR, or the RSTx.5 interrupts, you simply multiply the interrupt number by 8 to get the vector address. The following table presents the vector addresses for all possible interrupts... RST 0 - 00H RST 1 - 08H RST 2 - 10H RST 3 - 18H RST 4 - 20H TRAP - 24H RST 5 - 28H RST5.5 - 2CH RST 6 - 30H RST 6.5 - 34H RST 7 - 38H RST 7.5 - 3CH
RST is simply the opcode chosen to represent the Restart instruction.
The name, RST6.5, was chosen because the interrupt vector lies halfway between RST 6 and RST 7, specifically at address 0034H.