Merge pull request #729 from mrv96/patch-1

Support for custom TMSC buffer: cJTAG OScan1 improvement

doc/openocd.texi

@@ -2583,10 +2583,23 @@ and initially asserted reset signals.
 @end deffn
 
 @deffn {Command} {ftdi oscan1_mode} on|off
-Enable or disable OSCAN1 mode. This mode is intended for use with an adapter,
+Enable or disable OScan1 mode. This mode is intended for use with an adapter,
 such as the ARM-JTAG-SWD by Olimex, that sits in between the FTDI chip and the
-target. The adapter uses the normal JTAG signals to control TCKC and TMSC
+target. The cJTAG prococol is composed of two wires: TCKC (clock) and TMSC (data).
-(bidirectional) signals used in 2-wire cJTAG.
+TMSC is a bidirectional signal which is time-multiplexed alternating TDI, TMS and
+TDO. The multiplexing is achieved by a tri-state buffer which puts TMSC in Hi-Z
+when the device is supposed to take the control of the line (TDO phase).
+
+The ARM-JTAG-SWD adapter uses standard TRST and TMS signals to control TMSC
+direction. TRST is used by the adapter as selector for the multiplexers which set
+the JTAG probe in 2-wire mode. Whatever signal is used for this purpose, it must
+be defined with the name JTAG_SEL using @command{ftdi layout_signal}. JTAG_SEL is
+set to 0 during OScan1 initialization.
+
+Some JTAG probes like the Digilent JTAG-HS2, support cJTAG by using a
+separate pin to control when TMS is driven onto TMSC. You can use such
+probes by defining the signal TMSC_EN using
+@command{ftdi layout_signal TMSC_EN -data <mask>}.
 @end deffn
 
 @deffn {Command} {ftdi layout_signal} name [@option{-data}|@option{-ndata} data_mask] [@option{-input}|@option{-ninput} input_mask] [@option{-oe}|@option{-noe} oe_mask] [@option{-alias}|@option{-nalias} name]

src/jtag/drivers/ftdi.c

@@ -808,6 +808,8 @@ static void oscan1_mpsse_clock_data(struct mpsse_ctx *ctx, const uint8_t *out, u
 	static const uint8_t zero;
 	static const uint8_t one = 1;
 
+	struct signal *tmsc_en = find_signal_by_name("TMSC_EN");
+
 	LOG_DEBUG_IO("oscan1_mpsse_clock_data: %sout %d bits", in ? "in" : "", length);
 
 	for (unsigned i = 0; i < length; i++) {
@@ -833,8 +835,14 @@ static void oscan1_mpsse_clock_data(struct mpsse_ctx *ctx, const uint8_t *out, u
 			mpsse_clock_tms_cs_out(mpsse_ctx, &one, 0, 1, false, mode);
 		}
 
+		if (tmsc_en)
+			ftdi_set_signal(tmsc_en, '0'); /* put TMSC in high impedance */
+
 		/* drive another TCK without driving TMSC (TDO cycle) */
 		mpsse_clock_tms_cs(mpsse_ctx, &zero, 0, in, in_offset+i, 1, false, mode);
+
+		if (tmsc_en)
+			ftdi_set_signal(tmsc_en, '1'); /* drive again TMSC */
 	}
 }
 
@@ -845,6 +853,8 @@ static void oscan1_mpsse_clock_tms_cs(struct mpsse_ctx *ctx, const uint8_t *out,
 	static const uint8_t zero;
 	static const uint8_t one = 1;
 
+	struct signal *tmsc_en = find_signal_by_name("TMSC_EN");
+
 	LOG_DEBUG_IO("oscan1_mpsse_clock_tms_cs: %sout %d bits, tdi=%d", in ? "in" : "", length, tdi);
 
 	for (unsigned i = 0; i < length; i++) {
@@ -871,8 +881,14 @@ static void oscan1_mpsse_clock_tms_cs(struct mpsse_ctx *ctx, const uint8_t *out,
 			mpsse_clock_tms_cs_out(mpsse_ctx, &one, 0, 1, (tmsbit != 0), mode);
 		}
 
+		if (tmsc_en)
+			ftdi_set_signal(tmsc_en, '0'); /* put TMSC in high impedance */
+
 		/* drive another TCK without driving TMSC (TDO cycle) */
 		mpsse_clock_tms_cs(mpsse_ctx, &zero, 0, in, in_offset+i, 1, false, mode);
+
+		if (tmsc_en)
+			ftdi_set_signal(tmsc_en, '1'); /* drive again TMSC */
 	}
 }
 

tcl/interface/ftdi/digilent-hs2-cjtag.cfg

@@ -0,0 +1,19 @@
+# this supports JTAG-HS2 (and apparently Nexys4 as well)
+
+adapter driver ftdi
+ftdi device_desc "Digilent Adept USB Device"
+ftdi vid_pid 0x0403 0x6014
+
+ftdi channel 0
+ftdi layout_init 0xc0e8 0xe0eb
+
+reset_config none
+
+# These signals are used for cJTAG escape sequence on initialization only
+ftdi layout_signal TCK -data 0x0001
+ftdi layout_signal TDI -data 0x0002
+ftdi layout_signal TDO -input 0x0004
+ftdi layout_signal TMS -data 0x0008
+ftdi layout_signal JTAG_SEL -ndata 0xc000
+
+ftdi layout_signal TMSC_EN -data 0x0020