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:''See also [[Programming_the_Ethernet_controller|Programming the Ethernet Controller]]'' for a survey of modules and general discussion of FPGA design approach.''
:''See also [[Programming_the_Ethernet_controller|Programming the Ethernet Controller]]'' for a survey of modules and a general discussion of FPGA design approach.''
= (00X) Reset Modules =
= (00X) Reset Modules =
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Both Reset modules yield control to the Transmitter to deliver a status packet to the PC (state 101).
== Programming Details of Rest_hard ==
The Reset_hard module is written essentially as a list of module instantiations that perform EC control register read and write operations. The instances are "daisy-chained" to maintain chronological order - a "Done" signal from a preceding module is a "Go" for the following. Occasionally this list of instances is punctuated with counters intended to produce the required wait times and other specialized modules.
Programming the MAC interface requires the use of these specialized modules because the interface has an internal set of 16-bit control registers which are accessed indirectly through the use of general EC control registers. (See manual for more details.) The extra read/write operations necessary to use these indirect registers have been aggregated into ''MACwrToAddr'' in order to make this complication transparent to the higher level modules. These and other modules have in turn been used to create the ''MACaddrLoad'' module, which is responsible for loading the EC's factory-designated MAC address (stored in EC's flash memory) the above-mentioned indirect registers. This module also records a copy of these values in the [[FPGA_Registers#MAC_Register|MAC Address Register]] of the FPGA for the purpose of writing future packets.
Among other special modules, the ''INTcatcher'' is used to listen for "Self-Initialization Complete" interrupt (mask 0100). The Reset_hard block has also been instrumented with a dbShort external signal that "shorts out" the waiting counters for debig purposes.
=== Ports ===
=== Ports ===
[[FPGA_Registers#MAC_Register|MAC Address Register]] Control Lines
[[FPGA_Registers#MAC_Address_Registers|MAC Address Register]] Control Lines
* ''MACregs_En'': [out] register enable (write) signal
* ''MACregs_En'': [out] register enable (write) signal
* ''MACregs_A'': [out] byte address (4-bit)
* ''MACregs_A'': [out] byte address (4-bit)
* ''dbShort'': [in] debug signal to bypass EC reset waiting periods
* ''dbShort'': [in] debug signal to bypass EC reset waiting periods
== Programming Details of Rest_soft ==
Reset_soft works like a counter, triggering a "Go" signal for an ''AutoRd'' module instance. A write signal to the [[FPGA_Registers#MAC_Register|MAC Address Register]] is also triggered for the first six bytes (payload bytes three through eight) as these represent the MAC address of the PC. The following two bytes are the Debug Byte and Chip Reset Mask in that order. The reset signals to the DAC and/or the ADC are triggered immediately on the receipt of the Mask Byte.
=== Ports ===
* ''Clk'': [in] clock
Reset Signals
* ''Rst: [in] asynchronous reset
* ''DAC_iRst'': [out] active-low reset signal for the DAC chip.
* ''SPI_iRst'': [out] active-low reset signal for the SPI bus (i.e. for the ADC)
[[FPGA_Registers#State_Register|State Register]] Control Lines
* ''state_En'': [out] state register enable (write) signal
* ''state_D'': [out] (3-bit) state register input
* ''state_Q'': [in] (3-bit) state register output
[[FPGA_Registers#MAC_Register|MAC Address Register]] Control Lines
* ''MACregs_En'': [out] register enable (write) signal
* ''MACregs_A'': [out] byte address (4-bit)
* ''MACregs_D'': [out] 8-bit input value
* ''DBbyte'': [out] latched output bus that holds eight debug bits specified in the R' packet from PC. As of the time of writing this documentation, no use for these have been found.
[[FPGA_Transceiver|Transceiver]] Control Lines
* ''TxRx_Go'': [out] "Go" signal to read/write an EC control register byte
* ''TxRx_Aout'': [out] EC control register address (8-bit)
* ''TxRx_Dout'': [out] EC control register write value
* ''TxRx_RiW'': [out] active-high read, active-low write flag
* ''TxRx_Din'': [in] EC control register return value
* ''TxRx_Done'': [in] "Done" signal from [[FPGA_Transceiver|Transceiver]].