Merge branch 'feature/update_at_bin' into 'master'

feat: Update at bin for 512+512 map

See merge request sdk/ESP8266_NONOS_SDK!273

Author: xcguang

bin/at/512+512/user1.1024.new.2.bin

@@ -1,5 +1,13 @@
 # BOOT MODE
 ## download
+
+### Flash size 8Mbit: 512KB+512KB
+    boot_v1.2+.bin              0x00000
+    user1.1024.new.2.bin        0x01000
+    esp_init_data_default.bin   0xfc000 (optional)
+    blank.bin                   0x7e000 & 0xfe000
+
+
 ### Flash size 16Mbit-C1: 1024KB+1024KB
     boot_v1.2+.bin              0x00000
     user1.2048.new.5.bin        0x01000
@@ -61,4 +69,4 @@
 
     OK
 
-> NOTICE: If there are mistakes in the updating, then break update and print ERROR.
+> NOTICE: If there are mistakes in the updating, then break update and print ERROR.