140 SEI          ;NO INTERRUPIONS PLEASE
141 LDA #7E
143 STA FF00     ;RAM 1 WITH I/O VISIBLE
146 LDA #F1
148 STA D508     ;BIT 0 AT $D508 IS THE KEY TO THIS TRICK
151 LDA #20
153 STA D507     ;SWAP PAGES $00 AND $20
156 LDX #2       ;$00 AND $01 DON'T SWAP
158 STA 2000,X   ;STORE BLANKS AT "ORIGINAL" ZERO PAGE LOOP
161 INX
162 BNE 0158
164 LDA #0       ;RESTORE THE REGISTERS
166 STA D508
169 STA D507
172 STA FF00
175 BRK          ;RETURN TO MONITOR