# Xilinx Zynq-7020 boot media

The Zynq-7020's processing system is a dual Cortex-A9: ARMv7-A, 32-bit. It is the host for the
StarForth v4 mesh (`docs/v4.0.0/JUSTIFICATION.md` §5, §8).

Boot chain: BootROM, then `BOOT.BIN` (U-Boot SPL with the board's `ps7_init` DDR and clock setup),
then U-Boot, then LithosAnanke. Everything is read from the SD card's FAT partition.

Status: no image yet. `make boot_image TARGET=ZYNQ7020` stops with an error, because there is no
ARMv7 kernel port (`kernel/src/arch/armv7`: entry code, MMU, GIC, private timer). A trial
compile for Cortex-A9 built 147 of the 151 kernel and engine sources. The four that failed use
`__int128` or have no ARMv7 branch: `kernel/src/crypto/fe25519.c`,
`kernel/src/crypto/scalar25519.c`, `kernel/src/hal/hal.c` and
`v3/src/word_source/mixed_arithmetic_words.c`.

`BOOT.BIN` depends on the exact board (Zybo Z7-20, PYNQ-Z2, Arty Z7-20, ZedBoard, ...), because
`ps7_init` holds that board's DDR timing. The board has not been chosen yet.