If you are designing a system that requires bridging the gap between an ARM CPU and high-speed parallel hardware, master the GPMC. It is complex, it is finicky, but once you dial in those timing registers, it becomes an invisible, zero-wait-state extension of your CPU core.
Have you fought with GPMC timing lately? Keep a logic analyzer handy and always double-check your gpmc,clk-activation-ns values. If you are designing a system that requires
If you have ever needed to connect an FPGA, an old-school parallel ADC, an Ethernet controller, or even an external NOR flash to a processor without writing bit-banging GPIO code, the GPMC is your best friend. At its core, the GPMC is a hardware memory controller that acts as a bridge between the processor’s internal memory bus and external memory-mapped devices. To the CPU, reading from an external FPGA or writing to an LCD controller looks exactly like reading from a local RAM address—thanks to the GPMC. Keep a logic analyzer handy and always double-check
In the world of embedded Linux and high-performance microcontrollers, interfacing with external memory or peripheral chips often feels like a battle against timing constraints. Enter the GPMC (General Purpose Memory Controller). While it might not be as flashy as a GPU or as talked about as a PCIe bus, the GPMC is one of the most versatile and powerful peripherals found on Texas Instruments’ Sitara processors (like the AM335x, AM437x) and OMAP platforms. To the CPU, reading from an external FPGA
// Timing (values in nanoseconds or cycles) gpmc,sync-clk-ps = <10000>; gpmc,cs-on-ns = <0>; gpmc,cs-rd-off-ns = <60>; gpmc,cs-wr-off-ns = <60>; gpmc,oe-on-ns = <10>; gpmc,oe-off-ns = <50>; gpmc,we-on-ns = <10>; gpmc,we-off-ns = <50>; gpmc,adv-on-ns = <0>; gpmc,adv-rd-off-ns = <10>; gpmc,adv-wr-off-ns = <10>; }; }; The GPMC is the unsung hero of industrial embedded systems. In an era of high-speed serial interfaces, the parallel memory controller remains relevant because of its deterministic latency, raw bandwidth, and ability to memory-map custom FPGA logic.
