Method and system for reducing pin count in an integrated circuit when interfacing to a memory
View Patent ↗The invention provides a system and method for reducing pin count in an integrated circuit (IC) when interfacing to a synchronous dynamic random access memory (SDRAM). The SDRAM has a plurality of address lines and a plurality of data lines. The method includes connecting together the plurality of data lines and the plurality of address lines. The IC interfaces to the SDRAM through the connected plurality of address lines and the plurality of data lines.
1. A method of operating an interface for reducing pin count in an integrated circuit (IC) when interfacing with a synchronous dynamic random access memory chip (SDRAM), the SDRAM having a plurality of input address pins, a plurality of input/output data pins, and an internal memory, the IC having a set of data pins, comprising:
connecting together each one of the plurality of input/output data pins of the SDRAM to a respective one of the plurality of input address pins of the SDRAM to form a shared bus;
interfacing the IC to the SDRAM through the shared bus, wherein each line of the shared bus is connected to a respective one of the set of data pins of the IC, a respective one of the plurality of input address pins of the SDRAM, and a respective one of the plurality of input/output data pins of the SDRAM;
during a first clock cycle, sending a write command from the IC to the SDRAM via command lines to initiate a write operation at the SDRAM, sending an address for writing data via the shared bus from the set of data pins of the IC to the plurality of input address pins and the plurality of input/output data pins of the SDRAM, and asserting mask signals on mask lines by the IC such that the SDRAM does not write the address sent to the plurality of input/output data pins of the SDRAM as data for the write operation into the internal memory of the SDRAM;
during a second through M clock cycles, sending write data via the shared bus to the plurality of input address pins of the SDRAM and the plurality of input/output data pins of the SDRAM, and deasserting at least one of the mask signals on the mask lines by the IC, wherein the SDRAM writes the write data into the internal memory of the SDRAM; and
during an M+1 clock cycle, sending an activate command from the IC to the SDRAM along the command lines, sending a bank address via the shared bus from the set of data pins of the IC to the plurality of input address pins of the SDRAM and the plurality of input/output data pins of the SDRAM, and asserting the mask signals on the mask lines.
2. The method of claim 1 wherein the address for writing data is modified from an address to which data will be written during the write operation.
3. The method of claim 1 further comprising:
delaying the activate command until the write operation is complete.
4. The method of claim 1 , wherein M comprises a number of data blocks.
5. A method of operating an interface with for reducing pin count in an integrated circuit (IC) when interfacing with a synchronous dynamic random access memory chip (SDRAM) having a plurality of input address pins, a plurality of input/output data pins, and an internal memory, the IC having a set of data pins, comprising:
connecting together each one of the plurality of input/output data pins of the SDRAM to a respective one of the plurality of input address pins of the SDRAM to form a shared bus;
interfacing the IC to the SDRAM through the shared bus, wherein the shared bus is connected to the set of data pins of the IC, the plurality of input address pins of the SDRAM, and the plurality of input/output data pins of the SDRAM, wherein each of the set of data pins of the IC is connected to both a respective one of the input/output a data pins of the SDRAM and respective one of the input address pins of the SDRAM;
during a first clock cycle, sending a read command from the IC to the SDRAM via command lines to initiate a read operation at the SDRAM, sending an address for reading data via the shared bus from the set of data pins of the IC to the plurality of input address pins of the SDRAM and the plurality of input/output data pins of the SDRAM, and deasserting mask signals on mask lines by the IC,
wherein during a second clock cycle, the SDRAM prepares to read out data from the internal memory;
during a third through M clock cycles, receiving read data via the shared bus from the plurality of input/output data pins of the SDRAM to the set of data pins of the IC, and asserting the mask signals on the mask lines by the IC;
wherein during an M+1 clock cycle, the SDRAM exits the read operation;
during an M+2 clock cycle, sending an activate command from the IC to the SDRAM via the command lines, sending a first bank address via the shared bus from the set of data pins of the IC to the plurality of input address pins of the SDRAM and the plurality of input/output data pins of the SDRAM, and asserting the mask signals on the mask; and
during an M+3 clock cycle, sending a pre-charge command from the IC to the SDRAM via the command lines, sending a second bank address along the shared bus from the set of data pins of the IC to the plurality of input address pins of the SDRAM and the plurality of input/output data pins of the SDRAM, and asserting the mask signals on the mask lines by the IC such that the SDRAM does not write the second bank address received at the plurality of input/output data pins of the SDRAM into the internal memory of the SDRAM.
6. The method of claim 3 further comprising:
delaying the activate and the pre-charge commands until the read operation is complete.
7. The method of claim 3 , wherein M comprises a number of data blocks.
8. A system for reducing pin count in an integrated circuit (IC) when interfacing with a synchronous dynamic random access memory chip (SDRAM), comprising:
the SDRAM comprising a plurality of input address pins, a plurality of input/output data pins, and an internal memory, wherein each of the plurality of input/output data pins of the SDRAM is connected to a respective one of each of the plurality of input address pins of the SDRAM to form a shared bus;
the IC comprising a set of data pins that are each respectively connected on the shared bus to both a respective one of the plurality of input/output data pins of the SDRAM and a respective one of the plurality of input address pins of the SDRAM; and
a memory controller coupled to the set of data pins of the IC and configured to transmit data signals and address signals to the plurality of input/output data pins of the SDRAM and the plurality of input address pins of the SDRAM,
wherein during a first clock cycle, the memory controller sends a write command to the SDRAM to initiate a write operation at the SDRAM, sends an address for writing data via the shared bus to the plurality of input address pins of the SDRAM and the plurality of input/output data pins of the SDRAM, and asserting mask signals on mask lines such that the SDRAM does not write the address received at the plurality of input/output data pins of the SDRAM into the internal memory of the SDRAM,
wherein during a second through M clock cycles, the memory controller sends write data via the shared bus to the plurality of input address pins of the SDRAM and the plurality of input/output data pins of the SDRAM, and deasserts the mask signals on the mask lines wherein the SDRAM writes the write data into the internal memory of the SDRAM, and
wherein during an M+1 clock cycle, the memory controller sends an activate command to the SDRAM via the command lines, sends a bank address via the shared bus to the plurality of input address pins of the SDRAM and the plurality of input/output data pins of the SDRAM, and asserts at least one of the mask signals on the mask lines.
9. The system of claim 8 , wherein M comprises a number of data blocks.
10. A system for reducing pin count in an integrated circuit (IC) when interfacing with a synchronous dynamic random access memory (SDRAM), comprising:
the SDRAM comprising a plurality of input address pins, a plurality of input/output data pins, and an internal memory, wherein each of the plurality of input/output data pins of the SDRAM is connected to a respective one of each of the plurality of input address pins of the SDRAM to form a shared bus;
the IC comprising a set of data pins that are each respectively connected on the shared bus to both a respective one of the plurality of input/output data pins of the SDRAM and a respective one of the input address pins of the SDRAM; and
a memory controller coupled to the set of data pins of the IC and configured to transmit data signals and address signals to the plurality of input/output data pins of the SDRAM and the plurality of input address pins of the SDRAM,
wherein during a first clock cycle, the memory controller sends a read command to the SDRAM via command lines to initiate a read operation at the SDRAM, sends an address for reading data via the shared bus to the plurality of input address of the SDRAM pins and the plurality of input/output data pins of the SDRAM, and deasserts mask signals on mask lines,
wherein during a second clock cycle, the SDRAM prepares to read out data, from the internal memory of the SDRAM, to the shared bus, and the memory controller asserts the mask signals on the mask lines,
wherein during an M+1 clock cycle, the SDRAM exits the read operation,
wherein during an M+2 clock cycle, the memory controller sends an activate command to the SDRAM via the command lines, sends a first bank address along the shared bus to the plurality of input address pins of the SDRAM and the plurality of input/output data pins of the SDRAM, and asserts the mask signals on the mask lines such that the SDRAM does not write the first bank address received at the input/output data pins of the SDRAM into the internal memory of the SDRAM, and
wherein during an M+3 clock cycle, the memory controller sends a pre-charge command to the SDRAM via the command lines, sends a second bank address via the shared bus to the plurality of input address pins of the SDRAM and the plurality of input/output data pins of the SDRAM, and asserts at least one of the mask signals on the mask lines.
11. The system of claim 10 , wherein M comprises a number of data blocks.