pub fn wait_command_ready()Expand description
Spin until the GPU is ready to accept a new command word.
Polls GPUSTAT.READY_CMD. On real hardware this bit is briefly
cleared while the GPU is busy ingesting a multi-word packet; our
emulator forces it on, so the loop is essentially a single read.
Do not use this between GP0(0xA0) image payload words: after the
transfer setup packet, the GPU is waiting for data, not a new
normal command.