Specifications ispGDX80VA
In-System Programmability
All necessary programming of the ispGDXVA is done via when the pin is left unconnected, in which case the pin is
four TTL level logic interface signals. These four signals pulled high by the permanent internal pullup. This allows
are fed into the on-chip programming circuitry where a ISP programming and BSCAN testing to take place as
state machine controls the programming.
specified by the Instruction Table.
On-chip programming can be accomplished using an When the pin is driven low, the JTAG TAP controller is
IEEE 1149.1 boundary scan protocol. The IEEE 1149.1- driven to a reset state asynchronously. It stays there
compliant interface signals are Test Data In (TDI), Test while the pin is held low. After pulling the pin high the
Data Out (TDO), Test Clock (TCK) and Test Mode Select JTAG controller becomes active. The intent of this fea-
(TMS) control. The EPEN pin is also used to enable or tureistoallowtheJTAGinterfacetobedirectlycontrolled
disable the JTAG port.
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.
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,theJTAGTAPcontrollerisenabled.Thisisalsotrue
Figure 9. ispJTAG Device Programming Interface
TDO
TDI
ispJTAG
Programming
Interface
TMS
TCK
EPEN
ispGDX
ispLSI
80VA
ispGDX
80VA
Device
ispGDX
80VA
Device
ispMACH
Device
Device
Device
20
LATTICE [ LATTICE SEMICONDUCTOR ]
