ISPGDX240VA-9B388I Lattice Semiconductor, ISPGDX240VA-9B388I Datasheet - Page 18

• Manufacturer Part Number: ISPGDX240VA-9B388I
• Description: In-System Programmable 3.3V Generic Digital CrosspointTM
• Manufacturer: Lattice Semiconductor

All necessary programming of the ispGDXVA is done via
four TTL level logic interface signals. These four signals
are fed into the on-chip programming circuitry where a
state machine controls the programming.
On-chip programming can be accomplished using an
IEEE 1149.1 boundary scan protocol. The IEEE 1149.1-
compliant interface signals are Test Data In (TDI), Test
Data Out (TDO), Test Clock (TCK) and Test Mode Select
(TMS) control. The EPEN pin is also used to enable or
disable the JTAG port.
The embedded controller port enable pin (EPEN) is used
to enable the JTAG tap controller and in that regard has
similar functionality to a TRST pin. When the pin is driven
high, the JTAG TAP controller is enabled. This is also true
Figure 9. ispJTAG Device Programming Interface
In-System Programmability
TDO
TDI
TMS
TCK
EPEN
ispGDX
240VA
Device
ispJTAG
Programming
Interface
Device
ispLSI
18
ispMACH
when the pin is left unconnected, in which case the pin is
pulled high by the permanent internal pullup. This allows
ISP programming and BSCAN testing to take place as
specified by the Instruction Table.
When the pin is driven low, the JTAG TAP controller is
driven to a reset state asynchronously. It stays there
while the pin is held low. After pulling the pin high the
JTAG controller becomes active. The intent of this fea-
ture is to allow the JTAG interface to be directly controlled
by the data bus of an embedded controller (hence the
name Embedded Port Enable). The EPEN signal is used
as a “device select” to prevent spurious programming
and/or testing from occuring due to random bit patterns
on the data bus. Figure 9 illustrates the block diagram for
the ispJTAG interface.
Device
Specifications ispGDX240VA
ispGDX
Device
240VA
ispGDX
240VA
Device