better font rendering and start of z80 access

core_comm.h

@@ -0,0 +1,17 @@
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+
+// The RP2350 multicore FIFO holds eight 32-bit messages in each direction.
+// These functions intentionally enforce the sending/receiving core roles.
+
+// Try to send one word from core 1. Returns false instead of waiting when the
+// FIFO is full.
+bool core1_to_core0_try_write(uint32_t data);
+
+// Send one word from core 1, waiting until core 0 has made FIFO space.
+void core1_to_core0_write_blocking(uint32_t data);
+
+// Try to read one word on core 0. Returns false when no message is available.
+bool core0_try_read_from_core1(uint32_t *data);