0010            ;======================================================================
0010            
0010            ;----------------------------------------------------------------------
0010            ; 128-microsecond interrupt, Cext
0010            ; Unused. If this interrupt occurs, just push the accumulator (because
0010            ; ipret pops it) and re-enable the interrupts.
0010            ;----------------------------------------------------------------------
0010            
0010            DoNothing_ISR:
0010 2D    [05]      push A
0011                 ;Enable interrupts and return
0011 1A 20 [06]      mov A,[interrupt_mask]
0013 1E 20 [13]      ipret Global_Interrupt
0015            
0015            ;----------------------------------------------------------------------
0015            ; 1-millisecond interrupt
0015            ; Check to see if the chip is in suspend mode and take appropriate action.
0015            ; Copy values to Endpoint 1's buffer for sending.
0015            ;----------------------------------------------------------------------
0015            
0015            One_mSec_ISR:
0015 2D    [05]      push A
0016 2A 21 [05] iowr Watchdog
0018            ;Find out if enumeration is complete.
0018            ;If enumerating is in progress, loop_temp = 0.
0018 1A 37 [06]      mov A, [loop_temp]
001A 16 00 [04]      cmp A, 0h
001C            ;If enumeration is still in progress, jump.
001C A0 20 [05]      jz not_main
001E            ;Enumeration has ended, so decrement the loop counter
001E            ;(so it no longer = 0).
001E 27 37 [07]      dec [loop_temp]
0020            
0020            not_main:                         
0020            ;Check for bus activity.
0020 29 13 [05]      iord USB_Status_Control
0022 10 01 [04]      and A, 01h
0024 16 00 [04]      cmp A,0h
0026            ;If no bus activity, increment the suspend counter.
0026 A0 34 [05]      jz Inc_counter
0028            ;If bus activity detected, clear the bus-activity bit,
0028 29 13 [05]      iord USB_Status_Control
002A 10 FE [04]      and A, 0FEh
002C 2A 13 [05]      iowr USB_Status_Control
002E            ;and clear the suspend counter.
002E 19 00 [04]      mov A, 0h
0030 31 35 [05]      mov [suspend_counter], A
0032 80 57 [05]      jmp Suspend_end
0034            
0034            Inc_counter:
0034            ;Keep track of the amount of time with no bus activity.
0034 23 35 [07]      inc [suspend_counter]
0036            ;Get the number of milliseconds the bus has been idle.
0036 1A 35 [06]      mov A, [suspend_counter]
0038            ;Has it been 3 milliseconds?
0038 16 03 [04]      cmp A, 03h
003A            ;If no, there's nothing else to do.
003A B0 57 [05]      jnz Suspend_end
003C            ;If yes, put the chip in Suspend mode.
003C            ;Clear the Suspend counter.
003C 19 00 [04]      mov A, 0h
003E 31 35 [05]      mov [suspend_counter], A
0040            ;Enable pullups on Port 1; disable the output DAC.
0040 19 00 [04]      mov A, 0h
0042 2A 09 [05]      iowr Port1_Pullup
0044 19 FF [04]      mov A, 0ffh
0046 2A 01 [05]      iowr Port1_Data
0048            ;Set the Suspend bit. 
0048 29 FF [05]      iord Status_Control
004A 0D 08 [04]      or A, 08h
004C 2A FF [05]      iowr Status_Control
004E            ;The chip is now in Suspend mode. 
004E            ;On exiting Suspend mode, the chip will begin 
004E            ;executing instructions here:
004E 20    [04]      nop     
004F            ;Disable pullups on Port 1. Enable the output DAC.
004F 19 FF [04]      mov A, 0ffh
0051 2A 09 [05]      iowr Port1_Pullup
0053 19 00 [04]      mov A, 0h
0055 2A 01 [05]      iowr Port1_Data
0057            
0057            Suspend_end:
0057            ;Is endpoint 1 enabled?
0057 29 11 [05]      iord USB_EP1_TX_Config
0059 16 00 [04]      cmp A,0
005B            ;If no, do nothing.
005B A0 7D [05]      jz Select
005D            ;If yes, is start_send = 1?
005D            ;(Start_send adds a short delay after enumeration.)
005D 1A 32 [06]      mov A, [start_send]
005F 16 01 [04]      cmp A, 01h
0061            ;If no, do nothing
0061 B0 7D [05]      jnz Select
0063            ;If yes, send data:
0063 80 65 [05]      jmp send_value
0065            
0065            send_value:
0065            ;Copies values from RAM into Endpoint 1's buffer
0065            ;and enables sending the bytes on the next poll.
0065            
0065            ;disable Endpoint 1 interrupts
0065 1A 20 [06]      mov A,[interrupt_mask]
0067 10 EF [04]      and A, EFh
0069 31 20 [05]      mov [interrupt_mask],A
006B 2A 20 [05]      iowr Global_Interrupt
006D            
006D            ;Copy values from RAM to Endpoint 1's buffer for transmitting to the host.
006D            ;Two bytes:
006D 1A 38 [06]      mov A, [Data_Byte0]
006F 31 78 [05]      mov [Endpoint1_Byte0], A
0071 1A 39 [06]      mov A, [Data_Byte1]
0073 31 79 [05]      mov [Endpoint1_Byte1], A
0075            ;Add more bytes if the report format specifies it:
0075            ;     mov A, [Data_Byte2]
0075            ;     mov [Endpoint1_Byte2], A
0075            ;     mov A, [Data_Byte3]
0075            ;     mov [Endpoint1_Byte3], A
0075            ;     mov A, [Data_Byte4]
0075            ;     mov [Endpoint1_Byte4], A
0075            ;     mov A, [Data_Byte5]
0075            ;     mov [Endpoint1_Byte5], A
0075            ;     mov A, [Data_Byte6]
0075            ;     mov [Endpoint1_Byte6], A
0075            ;     mov A, [Data_Byte7]
0075            ;     mov [Endpoint1_Byte7], A
0075            
0075            ;Other things to try:
0075            ;Set the value at Port 0 to equal byte 0 in Endpoint 1's buffer:
0075            ;     iord Port0_Data
0075            ;     mov [Endpoint1_Byte0], A
0075            
0075            ;Or set a value here and copy to Endpoint 1's buffer, byte 1:
0075            ;     mov A, A5h
0075            ;      mov [Endpoint1_Byte1], A
0075            
0075            ;Configure Endpoint 1's transmit register 
0075            ;so that the bytes will transmit on the next poll.
0075 29 11 [05]      iord USB_EP1_TX_Config
0077            ;Don't change the Data 0/1 bit.
0077 10 40 [04]      and A,40h
0079            ;Set bits 4 and 7 to 1 enable transmitting.
0079            ;The low nibble is the number of data bytes (2).
0079 0D 92 [04]      or A,92h
007B 2A 11 [05]      iowr USB_EP1_TX_Config
007D            
007D            Select:
007D            ;Enable Endpoint 1 interrupts.
007D 1A 20 [06]      mov A,[interrupt_mask]
007F 0D 10 [04]      or A, 10h
0081 31 20 [05]      mov [interrupt_mask],A
0083 1E 20 [13]      ipret Global_Interrupt
0085            
0085            ;----------------------------------------------------------------------
0085            ;GPIO interrupt
0085            ;Can be configured to trigger when a port bit toggles.
0085            ;Unused here.
0085            ;----------------------------------------------------------------------
0085            
0085            GPIO_ISR:
0085 2D    [05]      push A
0086 2E    [05]      push X
0087            
0087 2C    [04]      pop X
0088 31 20 [05]      mov [interrupt_mask],A
008A 1E 20 [13]      ipret Global_Interrupt
008C            
008C            ;----------------------------------------------------------------------
008C            ;Endpoint 1 ISR
008C            ;Endpoint 1 can do IN (device to host) transfers only.
008C            ;This interrupt triggers when the host acknowledges
008C            ;receiving data from endpoint 1.
008C            ;The ISR toggles the data 0/1 bit for the next transaction and
008C            ;sets the EnableRespondToIN bit so the chip will respond to the 
008C            ;next poll of the endpoint.
008C            ;----------------------------------------------------------------------
008C            
008C            USB_EP1_ISR:
008C 2D    [05]      push A
008D            ;Toggle the data 0/1 bit so it's correct for the next transaction.
008D 29 11 [05]      iord USB_EP1_TX_Config  
008F 13 40 [04]      xor A,40h
0091            ;The interrupt clears the EnableRespondToIN bit (bit 7) in the TX Config.
0091            ;Set this bit to 1 so data will go out on the next poll.
0091 0D 92 [04]      or A, 92h
0093 2A 11 [05]      iowr USB_EP1_TX_Config
0095            ;Enable interrupts and return.
0095 1A 20 [06]      mov A, [interrupt_mask]
0097 1E 20 [13]      ipret Global_Interrupt
0099            
0099            ;----------------------------------------------------------------------
0099            ; Reset processing
0099            ; Triggers on Reset or "reserved" interrupt.
0099            ;To be safe, initialize everything.
0099            ;----------------------------------------------------------------------
0099            
0099            Reset:
0099            ;Place the data stack pointer at the lowest address of Endpoint 0's buffer.
0099            ;This keeps the stack from writing over the USB buffers.
0099            ;The USB buffers are in high RAM;
0099            ;the data stack pointer pre-decrements on a Push instruction.
0099            
0099 19 70 [04]      mov A, Endpoint_0
009B 30    [05]      swap A, dsp
009C            
009C            ;Initialize to FFh
009C 19 FF [04]      mov A, 0ffh
009E 2A 00 [05]      iowr Port0_Data                 ; output ones to port 0
00A0 2A 09 [05]      iowr Port1_Pullup               ; disable port 1 pullups
00A2                                                 ; select rising edge interrupts
00A2 2A 38 [05]      iowr Port1_Isink0               ; maximum isink current Port1 bit 0
00A4 2A 39 [05]      iowr Port1_Isink1               ; maximum isink current Port1 bit 1
00A6 2A 3A [05]      iowr Port1_Isink2               ; maximum isink current Port1 bit 2
00A8 2A 3B [05]      iowr Port1_Isink3               ; maximum isink current Port1 bit 3
00AA            
00AA            ;Initialize to 00h
00AA 19 00 [04]      mov A, 0h
00AC 2A 01 [05]      iowr Port1_Data                 ; output zeros to port 1
00AE 2A 04 [05]      iowr Port0_Interrupt            ; disable port 0 interrupts
00B0 2A 08 [05]      iowr Port0_Pullup               ; enable port 0 pullups
00B2 2A 30 [05]      iowr Port0_Isink0               ; minimum sink current Port0 bit 0
00B4 2A 31 [05]      iowr Port0_Isink1               ; minimum sink current Port0 bit 1
00B6 2A 32 [05]      iowr Port0_Isink2               ; minimum sink current Port0 bit 2
00B8 2A 33 [05]      iowr Port0_Isink3               ; minimum sink current Port0 bit 3
00BA 2A 34 [05]      iowr Port0_Isink4               ; minimum sink current Port0 bit 4
00BC 2A 35 [05]      iowr Port0_Isink5               ; minimum sink current Port0 bit 5
00BE 2A 36 [05]      iowr Port0_Isink6               ; minimum sink current Port0 bit 6
00C0 2A 37 [05]      iowr Port0_Isink7               ; minimum sink current Port0 bit 7
00C2 31 78 [05]      mov [Endpoint1_Byte0],A
00C4 31 79 [05]      mov [Endpoint1_Byte1],A
00C6 31 7A [05]      mov [Endpoint1_Byte2],A
00C8 31 29 [05]      mov [endpoint_stall], A
00CA 31 30 [05]      mov [remote_wakeup_status], A
00CC 31 31 [05]      mov [configuration_status], A
00CE 31 37 [05]      mov [loop_temp], A
00D0 31 32 [05]      mov [start_send], A
00D2 2A 21 [05]      iowr Watchdog                   ; clear watchdog timer
00D4            
00D4            ;initialize values to transmit at Endpoint 1.
00D4 19 A5 [04]      mov A, A5h
00D6 31 38 [05]      mov [Data_Byte0], A
00D8 19 F0 [04]      mov A, F0h
00DA 31 39 [05]      mov [Data_Byte1], A
00DC            
00DC            ;Enable Port 1, bit 0 interrupts.
00DC            ;     mov A, 01h
00DC            ;     iowr Port1_Interrupt
00DC            ;
00DC            ;Test what kind of reset occurred: bus or watchdog?
00DC 29 FF [05]      iord Status_Control
00DE            ;Was it a bus reset?
00DE 10 20 [04]      and A, USBReset
00E0            ;If yes, jump to handle it.
00E0 B0 F7 [05]      jnz BusReset
00E2 29 FF [05]      iord Status_Control
00E4            ;Was it a watchdog reset?
00E4 10 40 [04]      and A, WatchDogReset
00E6            ;If no, continue to wait for a bus reset
00E6 A0 F0 [05]      jz suspendReset
00E8            ;
00E8            ;Watchog reset:
00E8            ;A watchdog reset means that the watchdog timer
00E8            ;wasn't cleared for 8.192 milliseconds.
00E8            ;Wait for a bus reset to bring the system alive again.
00E8            ;Enable 1-millisecond interrupt only
00E8 19 04 [04]      mov A, TIMER_ONLY
00EA 31 20 [05]      mov [interrupt_mask],A
00EC 2A 20 [05]      iowr Global_Interrupt
00EE            ;Wait for a bus reset.
00EE            WatchdogHandler:
00EE 80 EE [05]      jmp WatchdogHandler
00F0            
00F0            suspendReset:
00F0            ;Return to suspend mode to wait for a USB bus reset.
00F0 19 09 [04]      mov A, 09h
00F2 2A FF [05]      iowr Status_Control