05-05-2022, 01:45 PM
Hello Under4Mhz
You may have to post your code for comment to start with.
Reading the status of the CRT controller at port 0x0c provides 3 bits of status information - one of these signifies that the CRT scan is in the
vertical blanking time. The Microbee doesn't normally have a way of generating an interrupt from this signal though. It's purely software polled.
There is however a link that can be done to the baseboard to generate an interrupt from the Z80 PIO when vertical Sync gets connected to one
of its port B I/O pins. This is how the psuedo real time clock operates in the ROM based Microbees.
You may have to post your code for comment to start with.
Reading the status of the CRT controller at port 0x0c provides 3 bits of status information - one of these signifies that the CRT scan is in the
vertical blanking time. The Microbee doesn't normally have a way of generating an interrupt from this signal though. It's purely software polled.
There is however a link that can be done to the baseboard to generate an interrupt from the Z80 PIO when vertical Sync gets connected to one
of its port B I/O pins. This is how the psuedo real time clock operates in the ROM based Microbees.