User busy indication

To enable the microcode to set the “PDAEMON is busy” flag without actually making any PDAEMON subunit perform computation, bit 4 of the falcon status register is connected to a dummy unit whose busy status is controlled directly by the user:

MMIO 0x420 / I[0x10800]: USER_BUSY
Read/write, only bit 0 is valid. If set, falcon status line 4 or 5 [USER] is set to 1 [busy], otherwise it’s set to 0 [idle].


what could possibly use PDAEMON’s busy status?