
90
Am79C978A
The PCI bus interface clock (CLK) is not required to be
running while the device is operating in Magic Packet
mode. Either of the INTA, the LED pins, or the PME sig-
nal may be used to indicate the receipt of a Magic
Packet frame when the CLK is stopped. If the system
wishes to stop the CLK, it will do so after enabling the
Magic Packet mode.
CAUTION:
To prevent unwanted interrupts from other
active parts of the controller, care must be taken to
mask all likely interruptible events during Magic Packet
mode. An example would be the interrupts from the
Media Independent Interface, which could occur while
the device is in Magic Packet mode.
IEEE 1149.1 (1990) Test Access Port
Interface
An IEEE 1149.1-compatible boundary scan Test Ac-
cess Port is provided for board-level continuity test
and diagnostics. All digital input, output, and input/
output pins are tested. The following paragraphs
summarize the IEEE 1149.1-compatible test func-
tions implemented in the controller.
Boundary Scan Circuit
The boundary scan test circuit requires four pins (TCK,
TMS, TDI, and TDO), defined as the Test Access Port
(TAP). It includes a finite state machine (FSM), an instruc-
tion register, a data register array, and a power-on reset
circuit. Internal pull-up resistors are provided for the TDI,
TCK, and TMS pins.
TAP Finite State Machine
The TAP engine is a 16-state finite state machine
(FSM), driven by the Test Clock (TCK), and the Test
Mode Select (TMS) pins. An independent power-on
reset circuit is provided to ensure that the FSM is in the
TEST_LOGIC_RESET state at power-up. Therefore,
the TRST is not provided. The FSM is also reset when
TMS and TDI are high for five TCK periods.
Supported Instructions
In addition to the minimum IEEE 1149.1 requirements
(BYPASS, EXTEST, and SAMPLE instructions), three ad-
ditional instructions (IDCODE, TRIBYP, and SETBYP)
are provided to further ease board-level testing. All un-
used instruction codes are reserved. See Table 21 for a
summary of supported instructions.
Table 21.
IEEE 1149.1 Supported Instruction
Summary
Instruction Register and Decoding Logic
After the TAP FSM is reset, the IDCODE instruction is
always invoked. The decoding logic gives signals to con-
trol the data flow in the data registers according to the
current instruction.
Boundary Scan Register
Each Boundary Scan Register (BSR) cell has two stages.
A flip-flop and a latch are used for the Serial Shift Stage
and the Parallel Output Stage, respectively. There are four
possible operation modes in the BSR cell shown in
Table 22.
Other Data Registers
Other data registers are the following:
1. Bypass register (1 bit)
2. Device ID register (32 bits) (See Table 23.).
CAUTION:
The content of the Device ID register is the
same as the content of CSR88.
Instruction
Name
Instruction
Code
Description
External
Test
ID Code
Inspection
Sample
Boundary
Force Float
Control
Boundary to
I/0
Bypass
Scan
Mode
Selected
Data
Register
EXTEST
0000
Test
BSR
IDCODE
0001
Normal
ID REG
SAMPLE
0010
Normal
BSR
TRIBYP
0011
Normal
Bypass
SETBYP
0100
Test
Bypass
BYPASS
1111
Normal
Bypass
Table 22.
BSR Mode Of Operation
1
2
3
4
Capture
Shift
Update
System Function
Table 23.
Device ID Register
Bits 31-28
Bits 27-12
Version
Part Number (0010 0110 0010 0110)
Manufacturer ID. The 11 bit manufacturer ID
cod for AMD is 00000000001 in accordance
with JEDEC publication 106-A.
Always a logic 1
Bits 11-1
Bit 0