Given SPI_CTRL_AUTOTX doesn't work on hardware it should be removed

[Yazwh0]

It adds cycles and ROM space unnecessarily.
(plus is has the wrong value!)

in dos/regs/inc.s

;-----------------------------------------------------------------------------
; Register bits
;-----------------------------------------------------------------------------
SPI_CTRL_SELECT_SDCARD = $01
SPI_CTRL_SELECT_MASK   = $01
SPI_CTRL_SLOWCLK       = $02
SPI_CTRL_AUTOTX        = $08
SPI_CTRL_BUSY          = $80

[Jaxartes]

Throwing in my 2¢:

It looks like the correct value of SPI_CTRL_AUTOTX should be $04 instead of $08, from https://github.com/fvdhoef/vera-module/blob/rev4/doc/VERA%20Programmer's%20Reference.md.

In https://github.com/fvdhoef/vera-module/blob/rev4/fpga/source/top.v the autotx bit does appear to be implemented (spi_autotx_r, spi_autotx_next). It looks like what it would do is transmit $FF whenever SPI_DATA gets read (without that, you'd have to write to SPI_DATA before reading anything).

It's not actually taking up any cycles or ROM space at the moment, since the code which uses it in dos/fat32/sdcard.s is not assembled without FAST_READ.

Perhaps someone with real hardware should try correcting SPI_CTRL_AUTOTX, uncommenting FAST_READ in dos/fat32/sdcard.s, assembling, and testing. Or perhaps X16 doesn't need the extra speed.