IMPACT_Custom_SRAM_03

University of South Alabama, IMPACT lab and VLSI lab design.

The chip contains three different custom memory designs: a 32x1024 6t SRAM, a 10x64 6t/4t SRAM, and a 2x2 Reram; built using Xschem and Magic EDA Tools. The chip is design to verify and validate the operations of the designs. All communications are routed to GPIO pins for external testing. The design allocates only 8 pins for Data-In, and 8 pins for Data-Out of the SRAMs; while 3 analog pins are used for the Reram. The remaining 14 pins are used for control.

32x1024 6T SRAM with flexible bit-truncation

Operation of this SRAM is controlled through GPIO. Four RTL modules are used to help with the control of the SRAM: An input register, a truncation decoder, a word-line decoder and an output mux.

The input register is used to manage and separate the inputs going into the memory, and the decoders. Input control is achieved by doing serial byte by byte transfer and saving of data. The inputs to this register are the project clock, the project register, a data enable signal, 2-bits for byte select, 2 bits for module select, and the 8 bit Data-In. The outputs of the register are send to the following modules depending on the values of byte and module select: 5 to 32 truncation decoder, 10 to 1024 wordline decoder, 32x1024 6T SRAM and 10x64 6t/4T SRAM.

The 5 to 32 truncation decoder controls which bits of the SRAM are going to be truncated. The inputs of the decoder are: a byte mode enable signal, a truncation enable, and the 5-bit input coming from the input register. The output of this module is a 32-bit bus going into the SRAM.

The 10x1024 Word-line decoder is used to select which word of the SRAM is going to be read to or write from. The inputs of this module are: a word-line enable signal, and the 10-bit input coming from the input register. The output of this module is a 10-bit bus going into the SRAM.

The output mux takes the 32-bit output of the SRAM and sends it byte-by-byte through the 8-bit Data-Out. Operation of this mux is control by the following signals: the byte select, module select, project clock, project reset, and the read enable signal.

Aside from the truncation managers built in this custom SRAM design, the memory works in a conventional way by relying on: a read enable signal to activate the sense amplifiers, a write enable signal to control the writing peripheral, the word enable coming from the word-line decoder and pre-charge signal for the bitlines.

10x64 6T/4T SRAM

This custom memory is a convination of 2 blocks, a 10x32 4T sram and a 10x32 4T SRAM. The inputs of the SRAM are: 10-bit data input coming from the input register, a precharge signal, 64-bit bus coming from the word-line decoder, a read enable, and a write enable. The 10-bit data out bus is connected to the output mux.

This particular design uses 2 different power supplies to allow for variable voltage across SRAM columns.

2x2 1T1R Reram array

This custom design is used for testing of the Reram cell on sky130B, it will be used as benchmark for future designs.

This design has 6 digital inputs that are borrowed from the 8-bit Data-In. To separate this inputs and avoid cross talk an RTL mux is used. The Reram also used 3 analog GPIO pins for the word, bit, and select lines.

Pin allocation

clk Project Clock GPIO pin 37 rst Project Reset GPIO pin 36 Data_In Byte Input for variable uses GPIO pin 35-28 Byte_Select Select Byte from word GPIO pin 27-26 Proj_Select Select Project GPIO pin 25-24 analog_io3 Reram Analog GPIO pin 23 analog_io2 Reram Analog GPIO pin 22 analog_io1 Reram Analog GPIO pin 21 WL_enable Enable signal Word Decoder GPIO pin 20 ByteMode_Enable Byte Mode Truncation (LOW) GPIO pin 19 Trunc_Enable Enable Truncation GPIO pin 18 PreCharge Precharge bitlines GPIO pin 17 DataIN_Enable Enable input change GPIO pin 16 WriteEnable SRAMs Write Enable signal GPIO pin 15 ReadEnable SRAMs Read Enable signal GPIO pin 14 Data_Out SRAMs Byte Output GPIO pin 13-6 ReramIn_Enable Reram Input Enable GPIO pin 5

Contributing Members (in no particular order)

• Dr. William (Liam) Oswald
• Md. Sajjad Hossain
• Safa Haq
• Md Omar Faruque
• Kyle Mooney
• Rafeeq Khan Mohammed
• Dr. Mario Renteria-Pinon

Principal Investigators: + Dr. Jinhui Wang + Dr. Na Gong

For any questions or inquiries please contact Mario at mrenteria@southalabama.edu