Hi all,
in the comment to the jtag_add_dr_scan() there is noted :
/**
* Generate a DR SCAN using the fields passed to the function.
* For connected TAPs, the function checks in_fields and uses fields
* specified there. For bypassed TAPs, the function generates a dummy
* 1-bit field. The bypass status of TAPs is set by jtag_add_ir_scan().
*/
void jtag_add_dr_scan(struct jtag_tap* tap, int num_fields,
const struct scan_field* fields, tap_state_t endstate);
Why is this dummy bit needed ?
When we shift out bits on TDO they will pass through the BYPASSed TAPs
and they wil all end up in our wanted TAP (which can be in the middle
of the scan chain), right ?
So then why do we need to shift out these extra bits, and not only the
bits we wanted to have in our targeted TAP ?
BR,
Drasko
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