AS91L1001

The AS91L1001 device provides an interface between the 60x bus on the Motorola MPC8260 processor and two  totally independent IEEE1149.1 interfaces, namely, the primary and secondary ports.

It handles all the protocol for the 60x bus to write and read directly to registers within the device with no additional glue logic.The AS91L1001 has three distinct modes of operation, namely Slave mode, Master mode, and 3^rd Party Support mode. These different modes control how data will be transferred on the IEEE1149.1 buses.

Slave mode: This is the default mode after the AS91L1001 has received a power-on reset. In this mode, there is a transparent connection between the primary and secondary JTAG ports. The processor interface is not used in the slave mode. This configuration is typically used to test a line card from a system back plane (the primary port is usually connected to the back plane and the secondary port is connected to the onboard JTAG chain). Once testing from the system back plane is completed, the AS91L1001 is reconfigured for master mode operation through a register. The master mode of operation is used to test the onboard JTAG chain, using the microprocessor interface.

Master mode: This mode is accessed via a command to a AS91L1001 register. The key feature of this mode is that both the Primary and Secondary are now both totally independent IEEE1149.1 bus masters, which enable concurrent operation on both the IEEE1149.1 channels. The Master mode enables the primary IEEE1149.1 channel to be used to access other PCB's connected via the 5-wire IEEE1149.1 interface on the back plane.

The secondary IEEE1149.1 port is used to test the card that is hosting the AS91L1001. This mode may be used for performing Interconnect testing or Flash/CPLD programming.