diff --git a/README.md b/README.md
index db921df..b401227 100644
--- a/README.md
+++ b/README.md
@@ -218,7 +218,10 @@ Pin meanings
 | 12 | O | /stop motor           |
 +----+---------------------------+
 ```
-It's recommended to pull-up at least **/scan media** pin to **VCC** via resistor (5K-10K) if you want to hot plug the FDSKey, because Twin Famicom has no pull-up resistors inside it. Also, don't forget to upgrade the FDSKey firmware to at least **v1.3**.
+
+You **must** pull-up **write data** line to **VCC** via resistor (5K-10K) if you want to save game progress, because Twin Famicom has no pull-up resistors inside it. Also, it's recommended to pull-up **/scan media** pin to **VCC** too if you want to hot plug the FDSKey.
+
+Also, don't forget to upgrade the FDSKey firmware to at least **v1.3**.
 
 
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