collapseos/blk/595

SPI relay driver

This driver is designed for a ad-hoc adapter card that acts as a
SPI relay between the z80 bus and the SPI device. When writing
to SPI_CTL, we expect a bitmask of the device to select, with
0 meaning that everything is de-selected. Reading SPI_CTL
returns 0 if the device is ready or 1 if it's still running an
exchange. Writing to SPI_DATA initiates an exchange.

Provides the SPI relay protocol. Load driver with "596 LOAD".
rc2014: separate SPI relay and SDC drivers My intention is to reuse the SPI relay to program AVR MCUs from a RC2014. 2020-06-30 08:48:00 +10:00			`SPI relay driver`

			`This driver is designed for a ad-hoc adapter card that acts as a`
Make the SPI Relay protocol support multiple devices Working on programming AVR chips exposes a glaring omission in my first design of the SPI Relay: not allowing multiple devices make this task hard. I constantly have to unplug my SD card before, plug the AVR chip holder, then play a bit, then unplug the AVR holder, then replug the SD card... My prototype for a SPI relay design is built, but I haven't tested it yet. I need to adapt the code first, which is what I do here. When the prototype is tested, I'll update the SDC recipe with a new schema. 2020-09-17 23:36:16 +10:00			`SPI relay between the z80 bus and the SPI device. When writing`
			`to SPI_CTL, we expect a bitmask of the device to select, with`
			`0 meaning that everything is de-selected. Reading SPI_CTL`
			`returns 0 if the device is ready or 1 if it's still running an`
			`exchange. Writing to SPI_DATA initiates an exchange.`
spi: add SPI_DELAY decl AVR chips often run at less than z80's system clock. This means that our SPI relay needs to have its own clock to properly communicate with it. This means that the delay between OUT and IN can't be hardcoded to 2 NOPs anymore. It needs to be configurable. 2020-08-23 21:55:17 +10:00
			`Provides the SPI relay protocol. Load driver with "596 LOAD".`