Thank Ernest,
The screen flicker mod on this bee only shortens the length of the flickers and does not impede the CPU allowing the CPU to run at full speed. It does it by allowing the 74LS166 Shift register to pump out its remain pixel contents onto the screen whilst the CPU is accessing the VDU/PCG RAM (unlike the original design which just clears its contents to black upon CPU access).
The SD Card interface makes use of the full speed SPI interface card (the 50way card to the left). The SPI interface has its own independent clock that can run at 20MHz.
This card was designed in 1985 as a mouse interface prior to the existence of the SPI moniker and subsequently adjusted to handle 3.3v peripherals such as SD Cards as needed.
The other little boards are SPI peripherals such as Serial UART, 8x 7 segment LED display and temperature sensor.
Access to the SPI devices is as easy as using MWBASIC with IN and OUT keywords.
The 50 way card on the right is the Roland MPU-401 MIDI interface. It was used to get the microbee to play drum machines and electronic synthesizers.
The large board in the centre is contains a Z80A DART, Z80A CTC, Z80A PIO, Baud rate generator, battery backed RTC, true RS232 level transmitters and receivers.
It was built prior to the design of the DRAM coreboard and was used to support split modem baud rates of 1200/75.
The CTC is extremely handy to as a time base and sound (tone) generator and interrupt controller.
The screen flicker mod on this bee only shortens the length of the flickers and does not impede the CPU allowing the CPU to run at full speed. It does it by allowing the 74LS166 Shift register to pump out its remain pixel contents onto the screen whilst the CPU is accessing the VDU/PCG RAM (unlike the original design which just clears its contents to black upon CPU access).
The SD Card interface makes use of the full speed SPI interface card (the 50way card to the left). The SPI interface has its own independent clock that can run at 20MHz.
This card was designed in 1985 as a mouse interface prior to the existence of the SPI moniker and subsequently adjusted to handle 3.3v peripherals such as SD Cards as needed.
The other little boards are SPI peripherals such as Serial UART, 8x 7 segment LED display and temperature sensor.
Access to the SPI devices is as easy as using MWBASIC with IN and OUT keywords.
The 50 way card on the right is the Roland MPU-401 MIDI interface. It was used to get the microbee to play drum machines and electronic synthesizers.
The large board in the centre is contains a Z80A DART, Z80A CTC, Z80A PIO, Baud rate generator, battery backed RTC, true RS232 level transmitters and receivers.
It was built prior to the design of the DRAM coreboard and was used to support split modem baud rates of 1200/75.
The CTC is extremely handy to as a time base and sound (tone) generator and interrupt controller.