Data Registers; Identification Code Register (Idcode) - Intel 386 User Manual

Intel386™ EX EMBEDDED MICROPROCESSOR USER'S MANUAL

18.2.4 Data Registers

The test-logic unit uses three data registers: bypass, identification code, and boundary-scan. The
instruction determines which data register is used.
The single-bit bypass register (BYPASS) provides a minimal-length serial path between TDI and
TDO. During board-level testing, you can use this path for any devices that are not currently un-
der test. This speeds access to the data registers for the devices that are being tested.
The 32-bit identification code register (IDCODE) identifies a device by manufacturer, part num-
ber, and version number. Figure 18-4 describes the register and shows the values for the Intel386
EX processor.
Identification Code Register
IDCODE
31
0 0
23
0 0
15
0 0
7
0 0
Bit Bit
Number Mnemonic
31–28 V3:0
27–12 PN15:0
11–1 MFR10:0
0 IDP
Figure 18-4. Identification Code Register (IDCODE)
18-8
1 0
1 0
0 0
0 1
Device version number.
Device part number.
Manufacturer identification (compressed JEDEC106-A code).
Identification Present. Always true for this device.
This is the first data bit shifted out of the device during a data scan
immediately following an exit from the test-logic-reset state. A one
indicates that an IDCODE register is present. (A zero originates from the
BYPASS register and indicates that the device being interrogated has no
IDCODE register.)
2027 0013H (3V)
Reset State: 2827 0013H (5V)
0 (3V) 0
1 (5V)
0 1
0 0
0 0
Function
24
0 0
16
1 1
8
0 0
0
1 1