K4R271869A

Figure 2 is a block diagram of the 128Mbit RDRAM device K4R271869A. The K4R271869A consists of two major blocks: a "core" block built from banks and sense amps similar to those found in other types of DRAM and a Direct RambusTM interface block which permits an external controller to access this core at up to 1.6GB/s.

Control Registers: The CMD, SCK, SIO0 and SIO1 pins appear in the upper center of Figure 2. They are used to write and read a block of control registers. These registers supply the RDRAM configuration information to a controller and they select the operating modes of the device.The nine bit REFR value is used for tracking the last refreshed row. Most importantly, the five bit DEVID specifies the device address of the RDRAM device on the Channel.

Clocking: The CTM and CTMN pins (Clock-To-Master)generate TCLK (Transmit Clock), the internal clock used to transmit read data. The CFM and CFMN pins (Clock-From-Master) generate RCLK (Receive Clock), the internal clock signal used to receive write data and to receive the ROW and COL pins.

DQA,DQB Pins: These 16 pins carry read (Q) and write (D) data across the Channel. They are multiplexed/de-multiplexed from/to two 64-bit data paths (running at one-eighth the data frequency) inside the RDRAM device.

Banks: The 16Mbyte core of the RDRAM device is divided into thirty two 0.5Mbyte banks, each organized as 512 rows, with each row containing 64 dualocts, and each dualoct containing 16 bytes. A dualoct is the smallest unit of data that can be addressed.

Sense Amps: The RDRAM device contains 34 sense amps. Each sense amp consists of 512 bytes of fast storage (256 for DQA and 256 for DQB) and can hold one-half of one row of one bank of the RDRAM device. The sense amp may hold any of the 512 half-rows of an associated bank.However, each sense amp is shared between two adjacent banks of the RDRAM device(except for sense amps 0, 15,16 and 31). This introduces the restriction that adjacent banks may not be simultaneously accessed.

RQ Pins: These pins carry control and address information.They are broken into two groups. RQ7..RQ5 are also called ROW2..ROW0, and are used primarily for controlling row accesses. RQ4..RQ0 are also called COL4..COL0, and are used primarily for controlling column accesses.

ROW Pins: The principle use of these three pins is to manage the transfer of data between the banks and the sense amps of the RDRAM device. These pins are de-multiplexed into a 24-bit ROWA (row-activate) or ROWR (row-peration)packet.

COL Pins: The principle use of these five pins is to manage the transfer of data between the DQA/DQB pins and the sense amps of the RDRAM device. These pins are demultiplexed into a 23-bit COLC (column-operation) packet and either a 17-bit COLM (mask) packet or a 17-bit COLX (extended-operation) packet.

ACT Command: An ACT (activate) command from an ROWA packet causes one of the 512 rows of the selected bank to be loaded to its associated sense amps (two 256 byte sense amps for DQA and two for DQB).

PRER Command: A PRER (precharge) command from an ROWR packet causes the selected bank to release its two associated sense amps, permitting a different row in that bank to be activated, or permitting adjacent banks to be activated.RD Command: The RD (read) command causes one of the 64 dualocts of one of the sense amps to be transmitted on the DQA/DQB pins of the Channel.

WR Command: The WR (write) command causes a dualoct received from the DQA/DQB data pins of the Channel to be loaded into the write buffer. There is also space in the write buffer for the BC bank address and C column address information. The data in the write buffer is automatically retired (written with optional bytemask) to one of the 64 dualocts of one of the sense amps during a subsequent COP command. A retire can take place during a RD, WR, or NOCOP to another device, or during a WR or NOCOP to the same device. The write buffer will not retire during a RD to the same device. The write buffer reduces the delay needed for the internal DQA/DQB data path turnaround.

PREC Precharge: The PREC, RDA and WRA commands are similar to NOCOP, RD and WR, except that a precharge operation is performed at the end of the column operation. These commands provide a second mechanism
for performing precharge.

PREX Precharge: After a RD command, or after a WR command with no byte masking (M=0), a COLX packet may be used to specify an extended operation (XOP). The most important XOP command is PREX. This command provides a third mechanism for performing precharge.