@Tim Edwards While working on the gpio defaults check, I came across some questions about the difference between these 2 modes (from https://github.com/efabless/caravel/blob/main/docs/rst/gpio.rst

GPIO_MODE_USER_STD_BIDIRECTIONAL:
The user project controls the GPIO pin. Pin is configured as a digital input or output. The input (io_in) is always active. The output (io_out) is applied to the pad only if the corresponding output disable (io_oeb) is set to zero.

GPIO_MODE_USER_STD_OUT_MONITORED:
The user project controls the GPIO pin like the GPIO_MODE_USER_STD_BIDIRECTIONAL mode, above; however, the pad value also appears at the management SoC, so the management SoC can treat this pad as an input pin, monitoring the value seen by the user project.

The values for these constants are

#define GPIO_MODE_USER_STD_BIDIRECTIONAL   0x1800
#define GPIO_MODE_USER_STD_OUT_MONITORED   0x1802

the only difference being that bit 1 is high for

GPIO_MODE_USER_STD_OUT_MONITORED

. However, bit 1 is

OUTPUT_DISABLE

. Looking at the verilog

gpio_control_block.v

/* Parameters defining the bit offset of each function in the chain */
    localparam MGMT_EN = 0;
    localparam OEB = 1;
...
            mgmt_ena <= gpio_defaults[MGMT_EN];
            gpio_holdover <= gpio_defaults[HLDH];
            gpio_slow_sel <= gpio_defaults[SLOW];
            gpio_vtrip_sel <= gpio_defaults[TRIP];
            gpio_ib_mode_sel <= gpio_defaults[MOD_SEL];
            gpio_inenb <= gpio_defaults[INP_DIS];
            gpio_outenb <= gpio_defaults[OEB];
...
    assign pad_gpio_outenb = (mgmt_ena) ? ((mgmt_gpio_oeb == 1'b1) ?
                        gpio_outenb : 1'b0) : user_gpio_oeb;

it appears that

OUTPUT_DISABLE

is only used when

MGMT_ENABLE

is high and

mgmt_gpio_oeb

is high. When

mgmt_ena

is high, the default value will override a high

mgmt_gpio_oeb

. Is that what was intended? If

MGMT_ENABLE

is low,

pad_gpio_outenb

is controlled solely by the

user_gpio_oeb

. I was expecting gpio modes with

OUTPUT_DISABLE

high to disable any output. Maybe something like

assign pad_gpio_outenb = (gpio_outenb) ? 1'b1 : ((mgmt_ena) ? mgmt_gpio_oeb : user_gpio_oeb);

As far as user input versus management input:

assign mgmt_gpio_in = pad_gpio_in;
...
    assign user_gpio_in = pad_gpio_in & gpio_logic1;

as long as the user area is powered, they will be the same level. In summary, 1. There appears to be no difference between

GPIO_MODE_USER_STD_BIDIRECTIONAL

and

GPIO_MODE_USER_STD_OUT_MONITORED

. Any enabled input signal appears in both the user area and management area. 2.

DM[2:0]

=

000

or

001

disable the output buffers, so for

INPUT_NOPULL

and

ANALOG

modes,

oeb

and

out

settings do not effect the output. Is that understanding correct?