diff --git a/main.cpp b/main.cpp
index 6fdbf23..77409b8 100644
--- a/main.cpp
+++ b/main.cpp
@@ -507,7 +507,7 @@ void print_help(const char* exe_name) {
         << "  tty:/tmp/ttyADC_data -> write a continuous legacy 4-word CH1/CH2 stream; with channels:1, CH2 is 0\n"
         << "  di1_group_avg -> with tty + di1:trace, emit one averaged 4-word step per constant DI1 run\n"
         << "  do1_toggle_per_frame -> hardware cyclic DO1 pattern in module memory:\n"
-        << "                         DO1 outputs 000111... continuously (toggle every 3 ADC ticks)\n"
+        << "                         DO1 outputs 00110011... continuously (toggle every 2 ADC ticks)\n"
         << "                         without per-tick DOUT updates from PC\n"
         << "  tty+di1_group_avg -> fast stream-only mode: skip CSV/SVG/live outputs and send only averaged tty data\n"
         << "  If sample_clock_hz is omitted together with clock:internal, the maximum ADC speed is used\n"
@@ -1033,7 +1033,7 @@ constexpr uint32_t kE502DiSyn2Mask =
 constexpr uint32_t kE502Digital1Mask = (static_cast<uint32_t>(1U) << 0U);
 constexpr uint32_t kE502Digital2Mask = (static_cast<uint32_t>(1U) << 1U);
 constexpr uint32_t kE502Do1Mask = (static_cast<uint32_t>(1U) << 0U);
-constexpr uint32_t kDo1TogglePeriodTicks = 3U;
+constexpr uint32_t kDo1TogglePeriodTicks = 2U;
 constexpr uint32_t kDo1CyclePatternWords = kDo1TogglePeriodTicks * 2U;
 constexpr uint32_t kStreamInputAdcFlag = 0x80000000U;
 constexpr uint32_t kStreamInputCalibratedAdcFlag = 0x40000000U;
@@ -1456,7 +1456,7 @@ int run(const Config& cfg) {
               << ((cfg.channel_count >= 2U) ? phy_channel_name(cfg.mode, cfg.ch2) : std::string("disabled")) << "\n"
               << "  DI1 handling: " << di1_mode_to_string(cfg.di1_mode) << "\n"
               << "  DO1 toggle per frame: "
-              << (cfg.do1_toggle_per_frame ? std::string("enabled (hardware cyclic 000111..., toggle every 3 ADC ticks)")
+              << (cfg.do1_toggle_per_frame ? std::string("enabled (hardware cyclic 00110011..., toggle every 2 ADC ticks)")
                                            : std::string("disabled")) << "\n"
               << "  DOUT rate: "
               << (cfg.do1_toggle_per_frame ? std::to_string(actual_dout_freq_hz) + " Hz" : std::string("disabled")) << "\n"