MAX 10 Flash programming

A little bit of overview info here, in chapter 2: https://www.altera.com/literature/ug/ug_usb_blstr.pdf

There is very little public documentation around on what goes in the CPLD as far as features/functionality. However, the Altera JAM STAPL (https://www.altera.com/support/support-resources/download/programming/jam.html) player does/did support using the USB Byte Blaster in simple JTAG bit banging mode. From the header comments in the jamstub.c routine:

/* The following code doesn't fully utilize the possibilities of the
 * USB-Blaster. It only buffers data up to a maximum packet size of 2 bytes.
 * The normal maximum packet size is up to 64 bytes (but would require a
 * major change to the logic of this program).
 *
 * Actually, the USB-Blaster offers a byte-shift mode to transmit up to 504 data
 * bits (bidirectional) in a single USB packet. A header byte has to be sent as
 * the first byte in a packet with the following meaning:
 *
 *   Bit 7 (0x80): Must be set to indicate byte-shift mode.
 *   Bit 6 (0x40): If set, the USB-Blaster will also read data, not just write.
 *   Bit 5..0:     Define the number N of following bytes
 *
 * All N following bytes will then be clocked out serially on TDI. If Bit 6 was
 * set, it will afterwards return N bytes with TDO data read while clocking out
 * the TDI data. LSB of the first byte after the header byte will appear first on TDI.
 */
/* Simple bit banging mode:
 *
 *   Bit 7 (0x80): Must be zero (see byte-shift mode above)
 *   Bit 6 (0x40): If set, you will receive a byte indicating the state of TDO in return.
 *   Bit 5 (0x20): Output Enable/LED.
 *   Bit 4 (0x10): TDI Output.
 *   Bit 3 (0x08): nCS Output (not used in JTAG mode).
 *   Bit 2 (0x04): nCE Output (not used in JTAG mode).
 *   Bit 1 (0x02): TMS Output.
 *   Bit 0 (0x01): TCK Output.
 *
 * For transmitting a single data bit, you need to write two bytes. Up to 64
 * bytes can be combined in a single USB packet.
 * It isn't possible to read a data without transmitting data.
 */

I have used this code as part of a custom JTAG scanner that employed the Altera USB Blaster as the hardware interface.