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ftd2jtag(n) 1.0 ftd2jtag "JTAG Control Interface"
ftd2jtag - JTAG Control via ftd2chan
TABLE OF CONTENTS
SYNOPSIS
DESCRIPTION
TRANSACTIONS
COMMANDS
VARIABLES
EXAMPLES
SEE ALSO
KEYWORDS
COPYRIGHT
package require Tcl 8.5
package require ftd2jtag ?1.0?
This manpage describes a set of commands that are used in conjunction
with the ftd2chan package to implement a JTAG control interface
via the MPSSE bitmode of the FTDI 2232 chip.
This package consists of an ensemble of commands that implement basic
JTAG scanning of data registers and executing JTAG instructions.
Note that the package only allows a single JTAG interface to be open
at a time.
Since JTAG uses serial bit streams to accomplish control,
often a large amount of I/O is needed to effect any control at all.
To that end, this package uses the normal Tcl channel buffering to
accumulate output and it reads input in a single operation.
In order to determine the I/O boundaries, the package implements a
transaction notion.
The ftd2jtag beginTrans and ftd2jtag endTrans commands
encapsulate an I/O transaction.
After invoking beginTrans, scripts are
presumed to contain invocations of the subcommands that make JTAG I/O
requests, namely:
- execInstr
- moveToState
- scanIn
- scanOut
- scanInOut
It is neither meaningful nor allowed for
the above commands to be executed outside of a transaction.
The transaction is terminated by invoking the endTrans subcommand,
at which time the output if flushed and the input is read.
- ftd2jtag open ?vid? ?pid? ?serialno? ?mask?
-
The open subcommand opens the USB device given by the
vid, pid and serialno using the ftd2chan command.
The channel is placed in MPSSE mode with mask as the I/O mask.
The default values for vid, pid, serialno and mask
are 0x403, 0xbcd9, {LM000001 A} and 0x8b, respectively.
These defaults correspond to opening a Luminary Micro LM3S811 Evaluation Board.
open also resets the JTAG TAP and sets the clocking frequency to
6 MHz.
- ftd2jtag close
-
The close subcommand closes the currently open USB JTAG device.
- ftd2jtag speed clkdiv
-
The speed sets the clock frequency of the FTDI 2232 chip.
The clkdiv argument is a 16-bit clock divisor and the final frequency
of the JTAG clocking is given by:
Clock Frequency = 12MHz / ((1 + clkdiv) * 2)
By default the ftd2jtag open command sets the clock frequency to 6 MHz
(i.e. clkdiv is set to 0).
- ftd2jtag reset ?bitno?
-
The reset subcommand forces a hard system reset by asserting
the I/O bit given by bitno and then deasserting it.
This command is only useful for system where a system line is tied to
one of the I/O pins of the FTDI 2232 chip.
The default value of bitno is 5 corresponding to the reset line
attachment of the Luminar Micro LM3S811 Evaluation Board.
- ftd2jtag resetTAP
-
The resetTAP subcommand drives the JTAG state machine from its
current state to the Test-Logic-Reset state
and resets all the internal state variables of the package.
This command is useful for recovering from errors and setting the TAP
and package internals to a well known state.
- ftd2jtag beginTrans
-
The beginTrans subcommand starts a JTAG I/O transaction.
See TRANSACTIONS for a description of the I/O model of this package.
- ftd2jtag endTrans
-
The endTrans subcommand terminates a JTAG I/O transaction.
See TRANSACTIONS for a description of the I/O model of this package.
This command returns a list of integer values that are the results
of the invocation of scanIn or scanInOut during the
transaction.
- ftd2jtag evalTrans script
-
The evalTrans subcommand is a convenience command that
evaluates script in the context of the
invoking procedure as if script were surrounded by invocations
of beginTrans and endTrans.
See TRANSACTIONS for a description of the I/O model of this package.
script may be an arbitrary Tcl script, but is presumed to
invoke package commands that post JTAG I/O requests.
After script is evaluated,
all JTAG output is flushed and any requested input is read.
This command returns a list of integer values requested by the invocations
of scanIn or scanInOut in script.
Transactions are not nestable.
- ftd2jtag execInstr instruction ?bits?
-
The execInstr subcommand moves the TAP to the Scan-IR state and
scans out the JTAG instruction given by instruction.
By default instructions are four bits long, but may specified to be bits
number of bits in length.
All JTAG instructions should be executed using this command because
it keeps a cache of the current value of the JTAG instruction
register and will elide superfluous Instruction Register scans
from the I/O stream.
- ftd2jtag moveToState state
-
The moveToState command clocks the JTAG TAP in order to arrive at
the state given by state.
state must be one of the six stable JTAG states given by:
- TLR ==> Test-Logic-Reset
- RTI ==> Run-Test/Idle
- SD ==> Shift-DR
- PD ==> Pause-DR
- SI ==> Shift-IR
- PI ==> Pause-IR
This command keeps track of the current JTAG TAP state and constructs the
necessary clocking of the Test Mode Selector (TMS) to arrive at the
requested state.
- ftd2jtag scanIn bits ?final?
-
The scanIn subcommand requests bits number of bits
of data be scanned in from the JTAG TAP while writing no output.
The final argument determines if this scan completes acquisition of
the underlying register, i.e. if the next JTAG operation will move to a
new TAP state.
If missing and by default final is true, indicating that the
invocation of scanIn completes the scanning of the register.
If final is false, then the scanIn is assumed to acquire only part
of the underlying register and subsequent scanning will occur before
moving to a new TAP state.
Each invocation of scanIn will result in one value containing the
requested number of bits being returned
from the enclosing evalTrans command.
The returned value contains the scanned bits as the least significant bits.
Using final allows parts of a register to be scanned into separate
values of the transaction.
- ftd2jtag scanOut value bits ?final?
-
The scanOut subcommand requests the least significant bits number of
bits of value be scanned out of the JTAG TAP while reading no output.
The final argument has the same meaning as for scanIn.
- ftd2jtag scanInOut value bits ?final?
-
The scanInOut subcommand requests the least significant bits
number of bits of value be scanned
out of the JTAG TAP while simultaneously reading bits number of
bits of input.
The final argument has the same meaning as for scanIn.
Each invocation of scanInOut will result in one value being returned
from the enclosing evalTrans command.
The variable ::ftd2jtag::ioDebug may be set to a value that
will cause trace output of the low level I/O.
This is primarily useful for debugging the ftd2jtag package
itself.
If ::ftd2jtag::ioDebug is set to 1, then a simple dump
of the raw I/O bytes to stdout is enabled.
If ::ftd2jtag::ioDebug is set to 2, then the debug output
includes information regarding how the JTAG TAP state changes are made
and how the input and output values are scanned.
The following examples assume that JTAG device has been opened using
ftd2jtag open command.
To read the IDCODE for a chip:
| |
set idcode [ftd2jtag evalTrans {
ftd2jtag execInst 0xe ; # IDCODE instruction value
ftd2jtag moveToState SD
ftd2jtag scanIn 32
}]
puts [format %#x $idcode]
==> 0x2ba00477 ; # IDCODE for the JTAG Debug Port on a LM3S811
|
To read the ARM Debug Access Port (a 35 bit register) on the LM3S811:
| |
set trans [ftd2jtag evalTrans {
ftd2jtag execInst 0xa ; # DPACC instruction
ftd2jtag moveToState SD
ftd2jtag scanOut 1 3 false ; # read request
ftd2jtag scanOut 0 32
ftd2jtag moveToState SD ; # scan again to get result
ftd2jtag scanIn 3 false ; # ack
ftd2jtag scanIn 32 ; # register read result
}]
==> 2 0 ; # OK acknowledgement value, 0 Debug Port value
|
ftd2chan
JTAG , USB
Copyright © 2007 by G. Andrew Mangogna