indeed, the ports at 00 and 01 and that pin 5 could be pullsed low by external logic to have the 6510 tristate it's bus pins so external logic could control the

indeed, the ports at 00 and 01 and that pin 5 could be pullsed low by external logic to have the 6510 tristate it's bus pins so external logic could control the bus, this was used by the VIC2 chip in the C64.