Method and apparatus for increasing the device count on a single ATA bus

In a device that includes ATA connection pins for connecting to corresponding signal lines in a single ATA bus, wherein the ATA connection pins include data lines, PDIAG and INTRQ connection pins, a method of operating the device, comprising:

• assigning an assigned identifier;
• receiving a selection command that includes a selection identifier from the data lines;
• comparing the selection identifier with the assigned identifier;
• waiting until PDIAG is negated and then asserting PDIAG and INTRQ in response to the selection identifier matching the assigned identifier;
• and
• tristating the data lines, PDIAG and INTRQ in response to the selection identifier not matching the assigned identifier.

In a device that includes ATA connection pins for connecting to corresponding signal lines in a single ATA bus, wherein the ATA connection pins include data lines, DASP, PDIAG and INTRQ connection pins, a method of operating the device, comprising:

• assigning an assigned identifier;
• receiving a selection command that includes a selection identifier from the data lines;
• comparing the selection identifier with the assigned identifier;
• waiting until PDIAG is negated and then asserting PDIAG and INTRQ in response to the selection identifier matching the assigned identifier and to determining that an ATA controller external to the device does not include additional hardware;
• and
• tristating the data lines, PDIAG and INTRQ in response to the selection identifier not matching the assigned identifier and to determining that the controller does not include the additional hardware.

In an ATA bus system that includes a controller, a single ATA bus and first and second devices, wherein the ATA bus is connected to the controller and the devices and includes data, PDIAG and INTRQ lines, the first device includes a first assigned identifier and the second device includes a second assigned identifier, a method of selecting one of the devices, comprising:

• the controller sending a selection command that includes a selection identifier across the data lines to the devices;
• the first device comparing the selection identifier with the first assigned identifier;
• the second device comparing the selection identifier with the second assigned identifier;
• and
• the first device asserting PDIAG and INTRQ in response to the selection identifier matching the first assigned identifier.

In an ATA bus system that includes a controller, a single ATA bus and first and second devices, wherein the ATA bus is connected to the controller and the devices and includes data, PDIAG and INTRQ lines, a method of selecting one of the devices, comprising:

• the first drive receiving a first assigned identifier;
• the second drive receiving a second assigned identifier;
• the controller sending a selection command that includes a selection identifier across the data lines to the devices;
• the first device comparing the selection identifier with the first assigned identifier;
• the second device comparing the selection identifier with the second assigned identifier;
• the first device waiting until PDIAG is negated and then asserting PDIAG and INTRQ in response to the selection identifier matching the first assigned identifier;
• and
• the second device tristating the data lines, PDIAG and INTRQ in response to the selection identifier not matching the second assigned identifier.

In an ATA bus system that includes a controller, a single ATA bus and first and second devices, wherein the ATA bus is connected to the controller and the devices and includes data, DASP, PDIAG and INTRQ lines, a method of selecting one of the devices, comprising:

• assigning a first assigned identifier to the first device;
• assigning a second assigned identifier to the second device;
• the controller sending a selection command that includes a selection identifier across the data lines to the devices;
• the first device comparing the selection identifier with the first assigned identifier;
• the second device comparing the selection identifier with the second assigned identifier;
• the first device waiting until PDIAG is negated by the second device and then asserting PDIAG and INTRQ in response to the selection identifier matching the first assigned identifier and to determining that the controller does not include additional hardware;
• and
• the second device tristating the data lines, PDIAG and INTRQ in response to the selection identifier not matching the second assigned identifier and to determining that the controller does not include the additional hardware.

In an ATA bus system that includes a controller, a single ATA bus and first and second devices, wherein the controller includes a selected status register, the ATA bus is connected to the controller and the devices and includes data lines and first and second DASP lines, the DASP lines are connected to the selected status register, the first device is connected to the first DASP line and includes a first assigned identifier and the second device is connected to the second DASP line includes a second assigned identifier, a method of selecting one of the devices, comprising:

• the controller sending a selection command that includes a selection identifier across the data lines to the devices;
• the first device comparing the selection identifier with the first assigned identifier;
• the second device comparing the selection identifier with the second assigned identifier;
• the first device asserting DASP in response to the selection identifier matching the first assigned identifier, thereby setting a first bit in the selected status register;
• and
• the controller reading the selected status register to verify that the first device is selected and the second device is not selected.

In an ATA bus system that includes a controller, a single ATA bus and first and second devices, wherein the controller includes a selected status register, the ATA bus is connected to the controller and the devices and includes data lines and first and second DASP lines, the DASP lines are connected to the selected status register, the first device is connected to the data lines and the first DASP line and includes a first assigned identifier and the second device is connected to the data lines and the second DASP line includes a second assigned identifier, a method of selecting one of the devices, comprising:

• the controller sending a selection command that includes a selection identifier across the data lines to the devices;
• the first device comparing the selection identifier with the first assigned identifier;
• the second device comparing the selection identifier with the second assigned identifier;
• the first device asserting DASP in response to the selection identifier matching the first assigned identifier, thereby setting a first bit in the selected status register;
• the second device negating DASP in response to the selection identifier not matching the second assigned identifier, thereby not setting a second bit in the selected status register;
• and
• the controller sending a read/write command across the ATA bus to the first device in response to reading the selected status register to verify that the first device is selected and the second device is not selected.

In an ATA bus system that includes a controller, a single ATA bus and first and second devices, wherein the controller includes a selected status register and an interrupt pending register, the ATA bus is connected to the controller and the devices and includes data lines, first and second DASP lines and first and second INTRQ lines, the DASP lines are connected to the selected status register, the INTRQ lines are connected to the interrupt pending register, the first device is connected to the data lines and the first DASP and INTRQ lines and includes a first assigned identifier and the second device is connected to the data lines and the second DASP and INTRQ lines includes a second assigned identifier, a method of selecting one of the devices, comprising:

• the controller sending a selection command that includes a selection identifier across the data lines to the devices;
• the first device comparing the selection identifier with the first assigned identifier;
• the second device comparing the selection identifier with the second assigned identifier;
• the first device asserting DASP in response to the selection identifier matching the first assigned identifier, thereby setting a first bit in the selected status register;
• the second device negating DASP in response to the selection identifier not matching the second assigned identifier, thereby not setting a second bit in the selected status register;
• and
• the controller sending a read/write command across the ATA bus to the first device in response to reading the selected status register to verify that the first device is selected and the second device is not selected.

In an ATA bus system that includes a controller, a single ATA bus and N devices, wherein the controller includes a selected status register, the ATA bus is connected to the controller and the devices and includes data lines and N DASP lines, the DASP lines are connected to the selected status register, the devices are each connected to the data lines and one of the DASP lines and disconnected from the other DASP lines such that each of the DASP lines is dedicated to one of the devices, the devices each include a unique assigned identifier, and N is an integer in the range of 3 to 8, a method of selecting one of the devices, comprising:

• the controller sending a selection command that includes a selection identifier across the data lines to the devices;
• the devices each comparing the selection identifier with its assigned identifier;
• the device that matches the selection identifier to its assigned identifier becoming a selected device that asserts DASP in response to the selection identifier matching its assigned identifier, thereby setting a corresponding bit in the selected status register;
• the other devices that each do not match the selection identifier to its assigned identifier becoming a non-selected device that negates DASP in response to the selection identifier not matching its assigned identifier, thereby not setting a corresponding bit in the selected status register;
• and
• the controller sending a read/write command across the ATA bus to the selected device in response to reading the selected status register to verify that the selected device is selected and the non-selected devices are not selected.