topic Using FlexIO to emulate i8080 bus on imx93 Linux in i.MX Processors

Using FlexIO to emulate i8080 bus on imx93 Linux

x10 — Thu, 14 Aug 2025 06:26:33 GMT

Hi, NXP TechSupport

I have implemented single beat write / read of i8080 bus cycle on imx93-EVK. The bus timing looks okay with total cycle time 800ns. There is a FASTACC bit in CTRL register, which suppose faster register access. But bus cycle becomes much longer instead of shorter with FASTACC bit enbaled. I suppose I haven't got right way to setup FASTACC bit. Please let me know to use the function of FASTACC bit in CTRL register. Thanks!

Regards

Cheng Shi

Re: Using FlexIO to emulate i8080 bus on imx93 Linux

joanxie — Thu, 14 Aug 2025 07:53:40 GMT

for FlexIO to drive 8080 bus, you can refer to the link as below

Using FlexIO to Drive 8080 Bus LCD on K32L2A

for the FASTACC bit, refer to the RM, You must enable the FLEXIO functional clock before accessing any of the FLEXIO registers. Provided the FLEXIO functional clock is at least equal to the bus clock, maybe you need check the functional clock

Re: Using FlexIO to emulate i8080 bus on imx93 Linux

x10 — Thu, 14 Aug 2025 08:17:55 GMT

As my understanding of RM, the flexio1's functional clock should be flexio1.flexio_clk (RM p.1744), is it right?

For FlexIO DTS :

flexio1: flexio@425c0000 {

compatible = "nxp,imx-flexio";

reg = <0x425c0000 0x10000>;

interrupts = <GIC_SPI 53 IRQ_TYPE_LEVEL_HIGH>;

clocks = <&clk IMX93_CLK_FLEXIO1_GATE>,

<&clk IMX93_CLK_FLEXIO1_GATE>;

clock-names = "per", "ipg";

assigned-clocks = <&clk IMX93_CLK_FLEXIO1_GATE>;

assigned-clock-parents = <&clk IMX93_CLK_FLEXIO1>;

....

};

the flexio functional clock is refered to "IMX93_CLK_FLEXIO1_GATE".

Both ipg_clk and per_clk are enabled in driver's probe function, but FASTACC behaviors weird.

Regards

Re: Using FlexIO to emulate i8080 bus on imx93 Linux

joanxie — Tue, 19 Aug 2025 06:26:02 GMT

refer to the RM, Provided the FLEXIO functional clock is at least equal to the bus clock, the CTRL[FASTACC] field can be set to support fast register accesses., so you also need to check the bus clock

Re: Using FlexIO to emulate i8080 bus on imx93 Linux

x10 — Tue, 19 Aug 2025 08:31:37 GMT

what is the bus clock in RM? Is it AXI clock or something similar?

Re: Using FlexIO to emulate i8080 bus on imx93 Linux

joanxie — Thu, 28 Aug 2025 08:05:25 GMT

bus clock means pclk, this should be the ipg clock, refer to the dts file, it seems the clock is set the same, you also can dump the clocks to check, I didn't find other request for FASTACC enable