st20-gp6 STMicroelectronics, st20-gp6 Datasheet - Page 121

• Manufacturer Part Number: st20-gp6
• Description: Gps Processor
• Manufacturer: STMicroelectronics

23 Test access port
The ST20-GP6 Test Access Port (TAP) conforms to IEEE standard 1149.1.
The TAP consists of five pins: TMS, TCK, TDI, TDO and notTRST.
The instruction register is 5 bits long, with no parity, and the pattern “00001” is loaded into the reg-
ister during the Capture-IR state.
There are four defined public instructions, see Table 23.1. All other instruction codes are reserved.
There are three test data registers; Bypass, Boundary-Scan and Identification. These registers
operate according to 1149.1. The Boundary-Scan register is not supported on the ST20-GP6.
0
0
0
1
Instruction code
a. MSB ... LSB; LSB closest to TDO.
0
0
0
1
0
0
0
1
0
1
1
1
0
0
1
1
a
Table 23.1 Instruction codes
EXTEST
IDCODE
SAMPLE/PRELOAD
BYPASS
Instruction
Boundary-Scan
Identification
Boundary-Scan
Bypass
Selected register
ST20-GP6
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