diff --git a/avr/flash.asm b/avr/flash.asm
new file mode 100644
index 0000000..a5574bc
--- /dev/null
+++ b/avr/flash.asm
@@ -0,0 +1,174 @@
+
+
+; ***************************************************************************
+; data
+
+
+.dseg
+
+flashDataBegin:
+  flashCurrentAddress:     .byte 2
+  flashLastReceivedMsg:    .byte 2
+flashDataEnd:
+
+
+
+
+; ***************************************************************************
+; code
+
+
+.cseg
+
+
+; ---------------------------------------------------------------------------
+; start flashing a page
+;
+; IN:
+; - Z: Address to work on (byte address as for LPM!)
+
+Flash_StartPage:
+  push zh
+    push zl
+      ldi r16, ((PAGESIZE*2)-1)
+      and r16, zl
+      rcall Flash_ReadPageIntoPageBuffer
+    pop zl
+  pop zh
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; finish flashing a page
+;
+; IN:
+; - Z: Address to work on (byte address as for LPM!)
+
+Flash_FinishPage:
+  ldi r16, ((PAGESIZE*2)-1)
+  and r16, zl
+  rcall Flash_ErasePage
+  rcall Flash_WritePage
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; Flash_ReadPageIntoPageBuffer
+;
+;
+; IN:
+; - Z: Address to read from (byte address as for LPM!)
+; OUT:
+; - nothing
+; MODIFIED REGISTERS: R0, R1, R15, R16, R20, R24, R25, Z
+
+Flash_ReadPageIntoPageBuffer:
+  in r15, SREG
+  cli
+    ldi r24, LOW(PAGESIZE*2)
+    ldi r25, HIGH(PAGESIZE*2)
+Flash_ReadPageIntoPageBuffer_loop:
+      lpm r0, Z+                                ; read source data from FLASH (low)
+      lpm r1, Z                                 ; read source data from FLASH (high)
+      sbiw ZH:ZL, 1                             ; rewind Z address for following SPM
+      ldi r20, (1<<SPMEN)                       ; enable next SPM, write into temp page buffer
+      rcall utilsDoSpm                          ; (R16)
+      adiw ZH:ZL, 2
+      sbiw r25:r24, 2                           ;use subi for PAGESIZEB<=256
+    brne Flash_ReadPageIntoPageBuffer_loop
+  out SREG, r15
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; Flash_WriteIntoPage
+;
+;
+; IN:
+; - Z: Address to write to (byte address as for LPM!)
+; - R1:R0: Word to write into page
+; OUT:
+; - Z: address for next write
+; MODIFIED REGISTERS: R15, R16
+
+Flash_WriteIntoPage:
+  in r15, SREG
+  cli
+  ldi r20, (1<<SPMEN)                       ; enable next SPM, write into temp page buffer
+  rcall utilsDoSpm                          ; (R16)
+  ldi r16, 2
+  add zl, r16
+  dec r16                                   ; doesn't affect carry flag
+  dec r16
+  adc zh, r16
+  out SREG, r15
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; Flash_ErasePage
+;
+;
+; IN:
+; - Z: Address of the page to erase.
+; OUT:
+; - nothing
+; MODIFIED REGISTERS: R0, R1, R15, R16, R18, R19, R20
+
+Flash_ErasePage:
+  in r15, SREG
+  cli
+    ldi r20, (1<<PGERS) + (1<<SPMEN)          ; enable next SPM, erase page (R1/R0 ignored)
+    rcall utilsDoSpm                          ; (R16)
+  out SREG, r15
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; Flash_WritePage
+;
+;
+; IN:
+; - Z: Address of the page to erase.
+; OUT:
+; - nothing
+; MODIFIED REGISTERS: R0, R1, R15, R16, R18, R19, R20
+
+Flash_WritePage:
+  in r15, SREG
+  cli
+    ldi r20, (1<<PGWRT) + (1<<SPMEN)          ; enable next SPM, write page (R1/R0 ignored)
+    rcall utilsDoSpm                          ; (R16)
+  out SREG, r15
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; utilsDoSpm
+;
+; wait until possible previous SPM finished and then issue another SPM.
+;
+; IN:
+; - R20: value for register SPMCR
+; - R0:  low value for SPM
+; - R1:  high value for SPM
+; - Z  : address for SPM (byte address!)
+; OUT:
+; - nothing
+; REGS: R16
+
+utilsDoSpm:
+wait:                ; wait for possibly previous SPM to complete
+    in r16, SPMCSR
+    sbrc r16, SPMEN
+  rjmp wait
+  ; SPM timed sequence
+  out SPMCSR, r20
+  spm
+  ret