1986BE91T: What is inside the Russian Arm?

    After previous articles with the insides of microcircuits ( 1 , 2 ), many wrote that photography is certainly interesting, but I would like to know what is what.

    Today, the opportunity to satisfy this natural interest has finally emerged. We will pick 1986VE91T - this is the Milander microcontroller based on the ARM Cortex-M3 core (officially licensed). Inside - 128 KiB of flash memory, 32 KiB of static memory, a hardware USB and 80 MHz core, made using 180nm technology.


    The wire connecting the terminals and pads on the chip remained: the casing is metal-ceramic, and it did not have to be etched. All the stuffing is hidden from our eyes in several layers of aluminum compounds. The size of the crystal is 6.54x5.9mm. We poison metallization ... Almost reached the bottom: And here is the bottom layer with transistors and a layer of polysilicon (the first level of connections and transistor gates):

    Crystal blocks abstract

    IO Cells & bonding pads - standard pieces of the circuit that control each leg of the microcircuit, contain elements of protection against static electricity, can switch to input and output mode. There are no transistors directly under the pads - as when welding the wire, they may be damaged.
    4x32KiB flash - 4 standard blocks of flash memory. Why not one big? The flash compiler could not generate memory with a bus wider than 32 bits, and for performance reasons, 128 was
    needed. 32KiB SRAM is a fast static memory whose state is not saved when the power is turned off.
    256x32B ROM - boot memory. It is programmed at the factory with "jumpers" - and cannot be changed.
    USB PHY- The physical interface of the USB protocol. There are only signal receivers / transmitters, and the digital part of the USB controller is in a synthesized "mess" in the center of the crystal.
    Internal linear regulator (1.8V) - an internal circuit for lowering the supply voltage to 1.8V. This is necessary because 1.8V transistors consume significantly less energy than 3.3V during operation.
    Battery domain - a battery-powered circuit designed for ultra-low power consumption. Here is a real-time timer, a few bytes of memory, a generator on an external 32kHz quartz.
    RC Oscillators - internal RC oscillators (low and high frequency), allowing the use of a microcontroller without quartz.
    System / USB PLL- Frequency multiplication schemes for the system and USB. They allow, for example, from 10 MHz quartz to get 80 MHz system frequency, and 48 MHz for USB.
    2xDAC - digital-to-analog converters.
    2xADC - analog-to-digital converters. Empty places - these were probably capacitors.
    2xCAN SRAM - small blocks of static memory. These are probably buffers for 2 CAN controllers and so on.

    Most of the above blocks are not required to be developed from scratch, but can be licensed at the factory, or purchased from companies developing and selling IP. But in this case, all the digital blocks (Timer, CAN, USB, RAM / ROM controllers, external bus, etc.), analog ADC, DAC, generators, PLL, built-in LDO, and even proprietary I / O pads, but only bought core, DMA, UART, SPI.

    Cell based synthesized logic is an automatically synthesized circuit from a Verilog description. Here, both the processor core itself and the peripheral controllers. The circuit is not synthesized directly from transistors, but from standard cells of a fixed height - implementing various functions like AND, OR, triggers, etc.

    Take a closer look at the individual elements.

    Boot ROM
    If desired, the contents can be "read". But of course, in this case it is not required, because Boot ROM is visible through the debugger. SRAM Cell area 9.14 μm 2 , corresponds to technology 180-250nm. Flash It’s immediately obvious why the flash is shoved into the microcontrollers a lot - the cell occupies a much smaller area (because you only need one transistor per bit, and sometimes half the transistor): Synthesized logic And here are the rows of standard cells, the main digital mince chip. Of course, it’s not possible to figure out what specific functions the cells perform here, because must see and metals.

    That's all for now, I hope my story was interesting. Well, in the future - I will try to disassemble the insides of any microcircuit in a simpler way already at the level of individual transistors.

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