IBM 3745 Series, Hardware Maintenance Reference

Page: 313 / 712

TRA Resets
Three functions are implemented to reset the TRA (TRM and TICs) or a part of the TRA:
1. The power-ON/tag reset function
2. The programmed reset function
3. The TIC reset function.
Power ON Reset and Tag Reset
These resets are activated in two ways:
1. By the power-ON reset line coming from the power blocks.
2. By the reset tag coming from the switch card.
It completely resets the TRA:
Ÿ All requests on the IOC bus are deactivated.
Ÿ The TRM reset bit is forced ON in the TRM control register (which indicates a reset has been done).
Ÿ
The TIC reset bits are forced ON (and the reset leads on the TIC bus) in the TIC control register.
Ÿ
All the interrupts and their associated statuses are reset.
Ÿ The disconnect bit and the CCU PIO disable bit are reset.
Ÿ The entire control logic is forced to idle state.
Ÿ The BR and IR scan wheel is pointed to the TIC 1.
Ÿ
More generally, all other functions and all other registers are forced in their inactive state.
Programmed Reset
The programmed reset is initiated by a PIO (IOH or MIOH). It allows the program to reset the TRM
without resetting the attached TIC(s) and the connect or disconnect state of the TRM.
The result is the same as the hardware reset except the TIC reset bits, the disconnect mode latch, and
the CCU PIO disabled latch are left in their current state.
TIC Reset
The program can perform a selective reset of the TIC by setting or resetting the TIC control register TIC
reset bit. The reset bits are connected to the TIC reset leads on the TIC bus. The reset lead is active as
long as the reset bit is ON in the TIC control register. The TIC reset lead causes the TIC to disconnect
itself from the ring and perform a reset.
Diagnostic Section TA0A
The TRM must be 'disconnected' before running the diagnostic section TA0A. The 'disconnect' command
must be performed after each power-OFF to power-ON.
Chapter 6. The Token-Ring Subsystem
6-19