SuperH (SH) 64-Bit RISC Series SH-5 System Architecture, Volume ...

PRELIMINARY DATA314 Debug and power management10.5.2 Debug module state with no tool connectedFor some applications, useful target system debugging can be performed without thetarget needing to be connected via SHDebug-Link or JTAG to a tool, that is, atraditional “monitor ROM” style debugger built into the application. In suchcircumstances, all on-chip debug resources must be enabled. Communication withresident debug code may occur via standard board-level interfaces such as a serialport or a LAN port.In such systems, the debug module enable/disable function is controlled by aboard-level jumper which either pulls the DM_ENABLE sensing pin (DM_CLKIN) low(DM enabled) or lets this signal be pulled high by its internal pull-up (DM disabled).10.5.3 Debug wakeup from standby stateWakeup via SHDebug-linkWhen SH-5 is in standby state, there are no clock pulses occurring on DM_CLKOUT.However, the tool can still generate clock pulses on the DM_CLKIN pin using atool-generated clock. This allows the debug tool to wakeup the system by sending awakeup message to the SH-5.This wakeup message consists of a normal DBUS message as defined in Volume 3Debug, Chapter 3 External Debug Interfaces. The act of receiving the DBUS messagewill wake the system, and the DBUS request will be processed as normal (that is, aDBUS response or error will be generated).Wakeup via JTAGSince the tool is the source of TCK clock, the TAP controller continues to operateeven when the chip is in standby state. A JTAG-connected tool can wake-up SH-5from standby state by shifting a special wakeup instruction into the sequence inthe debug DR register.The value of this wakeup instruction is implementation specific, and is defined inVolume 3 Debug, Chapter 4 Implementation specifics.D R A FTUse of the wakeup instruction when the JTAG port is not the active debuginterface causes undefined effects.Reception of the wakeup instruction when the JTAG port was previously selectedas the active debug interface asserts the wakeup signal to the PMU, and JTAG portremains as the active debug interface.SuperH, Inc.SH-5 System Architecture, Volume 1: System 05-SA-10001 v1.0