PCI SLOT signal definitions

PCI SLOT signal definitions
The PCI SLOT, or PCI expansion slot, utilizes a set of signal lines that enable communication and control between devices connected to the PCI bus. These signals are crucial for ensuring that devices can transfer data and manage their states according to the PCI protocol. Here are the main aspects of the PCI SLOT signal definitions:
Essential Signal Lines
1. Address/Data Bus (AD[31:0]):
This is the primary data transmission line on the PCI bus. It’s multiplexed to carry both addresses (during address phases) and data (during data phases) between the device and the host.
2. FRAME#:
Driven by the current master device, FRAME# indicates the start and duration of an access. Its assertion marks the beginning of a transfer, and its persistence indicates that data transmission continues. De-assertion signals the end of the last data phase.
3. IRDY# (Initiator Ready):
Indicates that the master device is ready to transfer data. During each clock cycle of data transfer, if the master can drive data onto the bus, it asserts IRDY#.
4. DEVSEL# (Device Select):
Driven by the targeted slave device, DEVSEL# signifies that the device is ready to respond to the bus operation. The delay in asserting DEVSEL# defines how long it takes the slave device to prepare to respond to a bus command.
5. STOP# (Optional):
An optional signal used to notify the master device to stop the current data transfer in exceptional cases, such as when the target device cannot complete the transfer.
6. PERR# (Parity Error):
Driven by the slave device to report parity errors detected during data transfer.
7. SERR# (System Error):
Used to report system-level errors that could cause catastrophic consequences, such as address parity errors or parity errors in special command sequences.
Control Signal Lines
1. Command/Byte Enable Multiplex (C/BE[3:0]#):
Carries bus commands during address phases and byte enable signals during data phases, determining which bytes on the AD[31:0] bus are valid data.
2. REQ# (Request to Use Bus):
Driven by a device wishing to gain control of the bus, signaling its request to the arbiter.
3. GNT# (Grant to Use Bus):
Driven by the arbiter, GNT# indicates to the requesting device that its request to use the bus has been granted.
Other Signal Lines
Arbitration Signals:
Include signals used for bus arbitration, ensuring fair allocation of bus resources among multiple devices requesting access simultaneously.
Interrupt Signals (INTA#, INTB#, INTC#, INTD#):
Used by slave devices to send interrupt requests to the host, notifying it of specific events or state changes.
In summary, the PCI SLOT signal definitions encompass a complex system of signal lines responsible for data transfer, device control, error reporting, and interrupt handling on the PCI bus. Although the PCI bus has been superseded by higher-performance PCIe buses, the PCI SLOT and its signal definitions remain significant in many legacy systems and specific applications.