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colognechip: Simplify handling of JTAG bypass bits #571

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Merged
trabucayre merged 1 commit into from
Jul 10, 2025
Merged

colognechip: Simplify handling of JTAG bypass bits #571

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19 changes: 4 additions & 15 deletions src/colognechip.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -324,25 +324,14 @@ void CologneChip::programJTAG_sram(const uint8_t *data, int length)

ProgressBar progress("Load SRAM via JTAG", length, 50, _quiet);

/* make sure to only send multiples of 8 bits */
int bits_before = _jtag->get_devices_list().size() - _jtag->get_device_index() - 1;
if (bits_before > 0) {
int n = 8 - (bits_before % 8);
uint8_t tx[n];
memset(tx, 0x00, n);
_jtag->shiftDR(tx, NULL, n, Jtag::SHIFT_DR);
}

/* the bypass register defaults to '0'.
* in order to generate a proper 'nop' command (0x00, 0xFF), send a
* sequence of zeros instead of ones.
*/
int bits_after = _jtag->get_device_index();
if (bits_after > 0) {
int n = (bits_after + 7) / 8;
uint8_t tx[n];
memset(tx, 0x00, n);
_jtag->shiftDR(tx, NULL, 8-bits_after, Jtag::SHIFT_DR);
if (_jtag->get_devices_list().size() > 1) {
int bits_before = 8 - (_jtag->get_device_index() % 8);
_jtag->set_state(Jtag::SHIFT_DR, 0);
_jtag->toggleClk(bits_before, 0);
}

Jtag::tapState_t next_state = Jtag::SHIFT_DR;
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