JTAG TAP Register Access

jtag-tap-reg.adoc

JTAG TAP Register Access

Instructions

Instruction	Opcode
WRITE_SINGLE	0b0000
WRITE_MULTIPLE	0b0001
READ_SINGLE	0b0010
READ_MULTIPLE	0b0011

Data Registers

• WRITE_REGISTER

• READ_REGISTER

Operations

Write Single

1. Send WRITE_SINGLE instruction.

   1. WRITE_REGISTER is selected.

   2. Access FSM goto SHIFT_ADDRESS.

2. Send 32-bit address to the WRITE_REGISTER.

   1. Address is latched.

   2. Access FSM goto SHIFT_DATA.

3. Send 32-bit data to the WRITE_REGISTER.

   1. Data is latched.

   2. Write is performed with latched address and data.

   3. Access FSM goto WRITE.

   4. Access FSM goto SHIFT_ADDRESS.

   5. User can go to step 2 or send another instruction.

Write Multiple

1. Send WRITE_MULTIPLE instruction.

   1. WRITE_REGISTER is selected.

   2. Access FSM goto SHIFT_ADDRESS.

2. Send 32-bit address to the WRITE_REGISTER.

   1. Address is latched.

   2. Access FSM goto SHIFT_DATA.

3. Send 32-bit data to the WRITE_REGISTER.

   1. Data is latched.

   2. Write is performed with latched address and data.

   3. Access FSM goto WRITE.

   4. Access FSM goto SHIFT_DATA.

   5. User can go to step 3 or send another instruction.