The logger will require a simple TLM 2.0 initiator socket, which will use the generic payload with a custom extension, JtagExtensionSC. The relevant headers are included.

#include <tlm.h>
#include <tlm_utils/simple_initiator_socket.h>

#include "JtagExtensionSC.h"
	  

The logger declares an initiator TLM 2.0 port to connect to the target port in the Or1ksim wrapper. This is the public interface to this module.

tlm_utils::simple_initiator_socket<JtagLoggerSC, 1>  jtag;
	  

A constructor is needed to connect the extension to the generic payload and to declare the SystemC thread generating JTAG transactions.

JtagLoggerSC (sc_core::sc_module_name  name);
	  

The module uses a single allocation of payload and extension. The temptation is to allocate and free these dynamically locally where they are needed. However, as noted earlier (see Section 11.2 this is an expensive operation in SystemC, so we have a single instance of each. The extension will be associated with the payload in the constructor.

tlm::tlm_generic_payload  payload;
JtagExtensionSC           ext;
	  

A SystemC thread is used to generate the traffic, and this is implemented in the private method, runJtag.

virtual void  runJtag();
	  

The JTAG registers for the Or1ksim debug unit have a complex structure. A set of utility methods is provided to construct the registers.

void  jtagReset (sc_core::sc_time &delay);

void  jtagInstruction (unsigned char     inst,
                       sc_core::sc_time &delay);

void  jtagSelectModule (unsigned char     moduleId,
                        sc_core::sc_time &delay);

void  jtagWriteCommand (unsigned char      accessType,
                        unsigned long int  addr,
                        unsigned long int  numBytes,
                        sc_core::sc_time  &delay);

void  jtagGoCommandRead (unsigned char      data[],
                         unsigned long int  dataBytes,
                         sc_core::sc_time  &delay);

// Utilities
unsigned long int   crc32 (unsigned long long int  value,
                           int                     num_bits,
                           unsigned long int       crc_in);

unsigned long long  reverseBits (unsigned long long  val,
                                 int                 len);
	  

The definition of the JTAG logger module class, JtagLoggerSC may be found in sys-models/jtag-soc/JtagLoggerSC.h in the distribution.