Load and Store instructions, refer to Chapter 5, “SCSI SCRIPTS

Instruction Set.”

2.2.9 JTAG Boundary Scan Testing

The LSI53C875A includes support for JTAG boundary scan testing in accordance with the IEEE 1149.1 specification with one exception, which is explained in this section. This device accepts all required boundary scan instructions including the optional CLAMP, HIGH-Z, and IDCODE instructions.

The LSI53C875A uses an 8-bit instruction register to support all boundary scan instructions. The data registers included in the device are the Boundary Data register, the IDCODE register, and the Bypass register. This device can handle a 10 MHz TCLK frequency for TDO and TDI.

Due to design constraints, the RST/ pin (system reset) always 3-states the SCSI pins when it is asserted. Boundary scan logic does not control this action, and this is not compliant with the specification. There are two solutions that resolve this issue:

1.Use the RST/ pin as a boundary scan compliance pin. When the pin is deasserted, the device is boundary scan compliant and when asserted, the device is noncompliant. To maintain compliance the RST/ pin must be driven HIGH.

2.When RST/ is asserted during boundary scan testing the expected output on the SCSI pins must be the HIGH-Z condition, and not what is contained in the boundary scan data registers for the SCSI pin output cells.

2.2.10SCSI Loopback Mode

The LSI53C875A loopback mode allows testing of both initiator and target functions and, in effect, lets the chip communicate with itself. When the Loopback Enable bit is set in the SCSI Test Two (STEST2) register, bit 4, the LSI53C875A allows control of all SCSI signals whether the chip is operating in the initiator or target mode. For more information on this mode of operation refer to the LSI Logic SCSI SCRIPTS Processor Programming Guide.

SCSI Functional Description

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LSI 53C875A technical manual Jtag Boundary Scan Testing, Scsi Loopback Mode