1. A data output clock generating circuit for a semiconductor memory apparatus, comprising:
a rising data output clock generating unit configured to combine a rising clock with a rising clock extraction signal generated in response to a rising output enable signal and a falling clock, to generate a rising data output clock; and
a falling data output clock generating unit configured to combine the falling clock with a falling clock extraction signal generated in response to a falling output enable signal and the rising clock, to generate a falling data output clock;
wherein the rising data output clock generating unit and the falling data output clock generating unit are independently driven in parallel,
wherein the rising data output clock generating unit is configured to generate the rising clock extraction signal being enabled at a time of a first rising edge of the falling clock after the rising output enable signal is enabled and being disabled at a time of a first rising edge of the falling clock after the rising output enable signal is disabled.
2. The data output clock generating circuit of claim 1,
wherein the rising data output clock generating unit is configured to extract the rising clock during a period when the rising clock extraction signal is enabled to generate the rising data output clock.
3. The data output clock generating circuit of claim 2,
wherein the rising data output clock generating unit includes:
a rising clock extraction signal generating section configured to receive the rising output enable signal and the falling clock to generate the rising clock extraction signal; and
a rising data output clock generating section configured to receive the rising clock extraction signal and the rising clock to generate the rising data output clock.
4. The data output clock generating circuit of claim 3,
wherein the rising clock extraction signal generating section includes:
an input section configured to receive the rising output enable signal and the falling clock to generate a set signal and a reset signal; and
a flip-flop configured to receive the set signal and the reset signal to generate the rising clock extraction signal.
5. The data output clock generating circuit of claim 1,
wherein the falling data output clock generating unit is configured to generate the falling clock extraction signal being enabled at a time of a first rising edge of the rising clock after the falling output enable signal is enabled and being disabled at a time of a first rising edge of the rising clock after the falling output enable signal is disabled.
6. The data output clock generating circuit of claim 5,
wherein the falling data output clock generating unit is configured to extract the falling clock during a period when the falling clock extraction signal is enabled to generate the falling data output clock.
7. The data output clock generating circuit of claim 6,
wherein the falling data output clock generating unit includes:
a falling clock extraction signal generating section configured to receive the falling output enable signal and the rising clock to generate the falling clock extraction signal; and
a falling data output clock generating section configured to receive the falling clock extraction signal and the falling clock to generate the falling data output clock.
8. The data output clock generating circuit of claim 7,
wherein the falling clock extraction signal generating section includes:
an input section configured to receive the falling output enable signal and the rising clock to generate a set signal and a reset signal; and
a flip-flop configured to receive the set signal and the reset signal to generate the falling clock extraction signal.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of assembling one of a multi-stage compressor and turbine for use in a gas-turbine engine, the method comprising the steps of: i) assembling a rotor drum so as to comprise a plurality of axially arranged rotor discs, ii) releasably connecting a plurality of static components to the assembled rotor drum, to form an intermediate structure, iii) inserting the intermediate structure within an outer casing, iv) fixing the plurality of static components to the outer casing, and v) releasing the static components from the rotor drum to permit rotation of the drum relative to the static components and the outer casing.
2. A method according to claim 1, wherein the casing is formed as a unitary component.
3. A method according to claim 1, wherein the step of assembling the rotor drum includes the step of welding the rotor discs to one another.
4. A method according to claim 1, wherein the step of assembling the rotor drum includes attaching a plurality of rotor blades to at least one of the rotor discs.
5. A method according to claim 1, wherein at least one of said rotor discs takes the form of an integrally bladed disc.
6. A method according to claim 1, wherein each static component is releasably connected to the rotor drum by at least one removable fixing element.
7. A method according to claim 6, wherein each said removable fixing element is inserted through a respective hole provided in the rotor drum, and is subsequently removed during said step of releasing the static components from the rotor drum.
8. A method according to claim 7, including the further step of closing said holes after removal of said fixing elements.
9. A method according to claim 6, comprising the step of mounting the rotor drum on an assembly mount, said fixing elements being releasably secured to the assembly mount.
10. A method according to claim 9, wherein at least part of the assembly mount is provided within the rotor drum, said fixing elements being provided to extend substantially radially outwardly from the mount.
11. A method according to claim 9, wherein the rotor drum is assembled on the assembly mount.
12. A method according to claim 1, wherein the rotor drum is assembled with its rotational axis oriented substantially vertically, the rotor drum remaining in said orientation during the step of releasably connecting the static components, and wherein said step of inserting the intermediate structure within the outer casing comprises lowering the outer casing over the intermediate structure.
13. A method according to claim 12, wherein the rotor drum is assembled with its smallest diameter rotor disc uppermost.
14. A method according to claim 1 comprising the further step of connecting the rotor drum to a shaft after the step of releasing the static components from the rotor drum.
15. A method according to claim 1, wherein each static component is provided with a substantially axially extending projection in its radially outermost region, and said step of fixing the static components to the outer casing comprises engaging each said projection in a slot provided inside the outer casing.
16. A method according to claim 1, wherein each static component is provided with a substantially radially extending tab at its radially outermost region, and said step of fixing the static components to the outer casing comprises rotating the outer casing relative to the intermediate structure so that each said radially extending tab becomes radially aligned with a respective inwardly directed tab provided inside the outer casing.
17. A method according to claim 16, wherein said step of rotating the outer casing relative to the intermediate structure involves rotation in the same direction to that in which rotational forces will act on the static components relative to the outer casing during operation of the compressor or turbine.
18. A method according to claim 16, wherein said step of inserting the intermediate structure within an outer casing involves moving each said inwardly directed tab axially past a respective said radially extending tab, prior to said rotation of the outer casing relative to the intermediate structure.
19. A method according to claim 16, wherein said outer casing is provided with inwardly directed abutments, each arranged to abut part of a static component when the radially extending tabs become aligned with respective inwardly directed tabs, thereby defining a limit to the rotation of the outer casing relative to the intermediate structure.
20. A gas turbine engine comprising a multi-stage turbine or compressor assembled according to the method of claim 1.