diff --git a/src/mame/drivers/dec8.cpp b/src/mame/drivers/dec8.cpp
index 5ed48a767b6..bc9d711032c 100644
--- a/src/mame/drivers/dec8.cpp
+++ b/src/mame/drivers/dec8.cpp
@@ -162,7 +162,7 @@ WRITE8_MEMBER(dec8_state::dec8_i8751_w)
 	case 0: /* High byte - SECIRQ is trigged on activating this latch */
 		m_i8751_value = (m_i8751_value & 0xff) | (data << 8);
 		m_mcu->set_input_line(MCS51_INT1_LINE, ASSERT_LINE);
-		m_i8751_timer->adjust(m_mcu->clocks_to_attotime(3)); // 3 clocks not confirmed
+		m_i8751_timer->adjust(m_mcu->clocks_to_attotime(64)); // 64 clocks not confirmed
 		break;
 	case 1: /* Low byte */
 		m_i8751_value = (m_i8751_value & 0xff00) | data;