isppac-powr1220at8 Lattice Semiconductor Corp., isppac-powr1220at8 Datasheet - Page 42

• Manufacturer Part Number: isppac-powr1220at8
• Description: In-system Programmable Power Supply Monitoring, Sequencing And Margining Controller
• Manufacturer: Lattice Semiconductor Corp.

Lattice Semiconductor
Programming ispPAC-POWR1220AT8: Alternate Method
Some applications require that the ispPAC-POWR1220AT8 be programmed before turning the power on to the
entire circuit board. To meet such application needs, the ispPAC-POWR1220AT8 provides an alternate program-
ming method which enables the programming of the ispPAC-POWR1220AT8 device through the JTAG chain with a
separate power supply applied just to the programming section of the ispPAC-POWR1220AT8 device with the main
power supply of the board turned off.
Three special purpose pins, VCCPROG, ATDI and TDISEL, enable programming of the un-programmed ispPAC-
POWR1220AT8 under such circumstances. The VCCPROG pin powers just the programming circuitry of the isp-
PAC-POWR1220AT8 device. The ATDI pin provides an alternate connection to the JTAG header while bypassing
all the un-powered devices in the JTAG chain. TDISEL pin enables switching between the ATDI and the standard
JTAG signal TDI. When the internally pulled-up TDISEL = 1, standard TDI pin is enabled and when the TDISEL = 0,
ATDI is enabled.
In order to use this feature the JTAG signals of the ispPAC-POWR1220AT8 are connected to the header as shown
in figure 32. Note: The ispPAC-POWR1220AT8 should be the last device in the JTAG chain.
Figure 1-34. ispPAC-POWR1220AT8 Alternate TDI Configuration Diagram
Alternate TDI Selection Via JTAG Command
When the TDISEL pin held high and four consecutive IDCODE instructions are issued, ispPAC-POWR1220AT8
responds by making its active JTAG data input the ATDI pin. When ATDI is selected, data on its TDI pin is ignored
until the JTAG state machine returns to the Test-Logic-Reset state.
This method of selecting ATDI takes advantage of the fact that a JTAG device with an IDCODE register will auto-
matically load its unique IDCODE instruction into the Instruction Register after a Test-Logic-Reset. This JTAG capa-
bility permits blind interrogation of devices so that their location in a serial chain can be identified without having to
know anything about them in advance. A blind interrogation can be made using only the TMS and TCLK control
pins, which means TDI and TDO are not required for performing the operation. Figure 1-35 illustrates the logic for
selecting whether the TDI or ATDI pin is the active data input to ispPAC-POWR1220AT8.
TDISEL
TMS
TDO
TCK
TDI
JTAG Signal
Connector
TDI
3. Sequenced Power
Supply Turn-on
Other JTAG
Device(s)
1-42
TDO
Supply Turn-On
2. Initial Power
ATDI
TDI
ispPAC-POWR1220AT8 Data Sheet
ispPAC-POWR
1220AT8
POWR1220AT8
Programming
1. Power for
TDO