Patent ID: 6957273

Claim:
A packet transmitting/receiving method for a computer system in which a plurality of packet transmitting/receiving units provided in correspondence to external modules are connected via a packet bus, in which each of said packet transmitting/receiving units is constructed in such a manner that when a packet received from said external module is transmitted, in the case where a transmitting request is issued and a transmission permission is obtained from a destination of a transmission, said packet is transmitted, and in the case where the transmission permission is not obtained, said packet is stored in a buffer and said unit is set into a transfer waiting state, and when the transmitting request of the packet is received from another packet transmitting/receiving unit, if said unit is in a packet receivable state, a response of the transmission permission is made and the packet is received, and if said unit is in a packet unreceivable state, the response of the transmission permission is inhibited, wherein with respect to the packet which is transmitted/received by said packet transmitting/receiving unit, whether a kind of packet is an internal register access packet, a response system packet, or a command system packet is discriminated, if said packet kind is determined to be said internal register access packet, said packet is stored into a first packet buffer in which a first priority has been set, if said packet kind is determined to be said response system packet, said packet is stored into a second packet buffer in which a second priority has been set, and further, if said packet kind is determined to be said command system packet, said packet is stored into a third packet buffer in which a third priority has been set, in the transfer waiting state where the command system packet to a certain transmission destination has been stored in said third packet buffer, in the case where the internal register access packet to the same transmission destination is received from said external module and stored in said first packet buffer, said packet transmitting/receiving unit removes the transfer waiting state of the command system packet of the low priority stored in said third packet buffer and transmits the response system packet of the high priority stored in said second packet buffer, and in a response inhibiting state of the transmission permission caused by an error of the external module, in the case where the transmitting request of the internal register access packet of the highest priority is received, said packet transmitting/receiving unit on the transmission destination side makes a response of the transmission permission, receives the internal register access packet, and returns an error detail information packet showing an error state of the external module.