CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a divisional of U.S. application Ser. No. 13/719,018, filed Dec. 18, 2012, which claims priority under 35 U.S.C 119(a) to Korean Application No. 10-2012-0090934, filed on Aug. 20, 2012, in the Korean Intellectual Property Office, the contents of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     Embodiments of the present disclosure relate to semiconductor memory devices. 
     Computer systems or electronic communication systems continue to advance in parallel with increases in the storage capacity and lower fabrication cost of the semiconductor memory devices used in such systems. In particular, a high integration density of the semiconductor memory devices may lead to a high capacity of data storage thereof. The semiconductor memory devices, for example, dynamic random access memory (DRAM) devices may be configured to include a plurality of word lines and a plurality of bit lines which are arrayed in rows and columns to intersect each other, and a plurality of memory cells may be disposed at respective ones of cross points of the word lines and the bit lines. Each of the memory cells of the DRAM devices may be configured to include a single cell transistor and a single capacitor, and the memory cells of the DRAM devices may constitute one or more cell blocks. Operations of the DRAM devices may be briefly described hereinafter. 
     If a complementary (e.g., inversed) row address strobe (/RAS) signal is enabled during an active operation, a row address signal supplied through a row address buffer may be decoded to execute a row decoding operation that selects one of word lines in a cell block. In such a case, if data in memory cells electrically connected to the selected word line are loaded on bit line pairs including bit lines and complementary bit lines, a signal informing of a point of time that sense amplifiers operate may be enabled to drive a sense amplifier drive circuit of a cell block which is selected by the row address signal. In addition, bias potentials of the sense amplifiers may be changed into a core potential (Vcore) or a ground potential (Vss) by the sense amplifier drive circuit, and the sense amplifiers may operate. If the sense amplifiers operate, a small potential difference between a bit line potential and a complementary bit line potential may be amplified to have a large potential difference. 
     Subsequently, if a read operation is executed, at least one of the bit line data amplified by the sense amplifiers may be transmitted to an input/output (I/O) line through a column transfer transistor which is selected and turned on by a column address signal. Meanwhile, if a write operation is executed, a data supplied through the I/O line may be loaded on the bit line through the column transfer transistor which is selected and turned on by a column address signal, and the data on the bit line may be stored in a memory cell through at least one of cell transistors which are turned on by a selected word line. 
     As described above, the semiconductor memory devices may operate in a write mode to store data into the memory cells, or a read mode to read out the data stored in the memory cells. When the write operation and the read operation are executed, a plurality of internal signals may be generated in the semiconductor memory device. 
     SUMMARY 
     Example embodiments are directed to semiconductor memory devices. 
     According to some embodiments, a semiconductor memory device includes a first data I/O block and a second data I/O block. The first data I/O block executes a write operation to transmit a first input data supplied through a first pad to a first global I/O line, and further generates a write internal signal. The second data I/O block transmits the write internal signal to a second pad in response to a monitor enable signal. 
     According to further embodiments, a semiconductor memory device includes a first data I/O block and a second data I/O block. The first data I/O block executes a read operation thereby causing the data on a first global I/O line to be supplied to a first pad. The first data I/O block generates a read internal signal during the read operation. The second data I/O block transmits the read internal signal to a second pad in response to a monitor enable signal. 
     According to further embodiments, a semiconductor memory device includes a first data input block, a second data input block and a data I/O block. The first data input block buffers a first input data supplied through a first pad to generate a first internal input data. In addition, the first data input block executes a first write operation to load the first internal input data on a first global I/O line. Moreover, the first data input block generates a write internal signal during the first write operation. The second data input block buffers a second input data supplied through a second pad to generate a second internal input data. The second data input executes a second write operation to load the second internal input data on a second global I/O line. The data I/O block transmits the write internal signal to a third pad in response to a monitor enable signal. The data I/O block executes a third write operation to load the second internal input data on a third global I/O line. 
     A method of operating a semiconductor memory device, in accordance with one embodiment of the present invention includes, in part, executing a write operation to transmit a first input data from a first pad to a first global I/O line, generating a write internal signal during the write operation, and transmitting the write internal signal to a second pad in response to a monitor enable signal. 
     A method of operating a semiconductor memory device, in accordance with another embodiment of the present invention includes, in part, performing a read operation to supply a data from a first global I/O line to a first pad, generating a read internal signal, and transmitting the read internal signal to a second pad in response to a monitor enable signal. 
     A method of operating a semiconductor memory device, in accordance with another embodiment of the present invention includes, in part, buffering a first input data supplied through a first pad to generate a first internal input data, loading the first internal input data onto a first global I/O line during a first write operation, generating a write internal signal during the first write operation, buffering a second input data supplied through a second pad to generate a second internal input data, executing a second write operation to load the second internal input data on a second global I/O line, transmitting the write internal signal to a third pad in response to a monitor enable signal, and executing a third write operation to load the second internal input data onto a third global I/O line. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the inventive concept will become more apparent in view of the attached drawings and accompanying detailed description, in which: 
         FIG. 1  is a block diagram of a semiconductor memory device, according to one embodiment; 
         FIG. 2  is a circuit diagram of an example of the first monitor signal generator of the semiconductor memory device of  FIG. 1 ; 
         FIG. 3  is a circuit diagram of an example of the first output unit of the semiconductor memory device of  FIG. 1 ; 
         FIG. 4  is a block diagram of a semiconductor memory device, according to another embodiment; 
         FIG. 5  is a block diagram of a semiconductor memory device, according to yet another embodiment of the present invention; and 
         FIG. 6  is a circuit diagram of an example of the selection input unit of the semiconductor memory device of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of the inventive concept will be described hereinafter with reference to the accompanying drawings. However, the embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the inventive concept. 
       FIG. 1  is a block diagram of a semiconductor memory device according to one embodiment. 
     As illustrated in  FIG. 1 , semiconductor memory device may be configured to include a first data I/O block  1  and a second data I/O block  2 . The first data I/O block  1  may be configured to include a first pad  11 , a first input buffer  12 , a first write path unit  13 , a first read path unit  14 , a first monitor signal generator  15  and a first output unit  16 . The second data I/O block  2  may be configured to include a second pad  21 , a second input buffer  22 , a second write path unit  23 , a second read path unit  24 , a second monitor signal generator  25  and a second output unit  26 . 
     The first input buffer  12  may buffer a first input data DIN 1  supplied through the first pad  11  to generate a first internal input data INT_DIN 1  when the first data I/O block  1  operates in a write mode. The first write path unit  13  may drive a first global I/O line GIO 1  to transmit the first internal input data INT_DIN 1  to the first global I/O line GIO 1  when the first data I/O block  1  operates in the write mode. The first write path unit  13  may also generate and output a write internal signal WT_INT when the first internal input data INT_DIN 1  is transmitted to the first global I/O line GIO 1 . The first read path unit  14  may receive first internal output data RDATA 1  and FDATA 1  from data loaded on the first global I/O line GIO 1  when the first data I/O block  1  operates in a read mode. The first monitor signal generator  15  may buffer a read internal signal RD_INT to generate a first monitor signal MS 1  when a monitor enable signal M_EN is enabled. The first output unit  16  may selectively output the first internal output data RDATA 1  and FDATA 1  or the first monitor signal MS 1  as a first output data DOUT 1  in response to the monitor enable signal M_EN. The first output data DOUT 1  may be supplied through the first pad  11 . The first output unit  16  may output the first monitor signal MS 1  as the first output data DOUT 1  when the monitor enable signal M_EN is enabled. The first output unit  16  may output the first internal output data RDATA 1  and FDATA 1  as the first output data DOUT 1  in synchronization with internal clock signals RCLK and FCLK when the monitor enable signal M_EN is disabled. The monitor enable signal M_EN may be enabled to monitor the write internal signal WT_INT and the read internal signal RD_INT. The second input buffer  22  may buffer a second input data DIN 2  supplied through the second pad  21  to generate a second internal input data INT_DIN 2  when the second data I/O block  2  operates in a write mode. The second write path unit  23  may transmit the second internal input data INT_DIN 2  to a second global I/O line GIO 2  when the second data I/O block  2  operates in the write mode. The second read path unit  24  may receive second internal output data RDATA 2  and FDATA 2  from data loaded on the second global I/O line GIO 2  when the second data I/O block  2  operates in a read mode. The second read path unit  24  may also generate and output the read internal signal RD_INT when the second internal output data RDATA 2  and FDATA 2  are extracted from the data loaded on the second global I/O line GIO 2 . The second monitor signal generator  25  may buffer the write internal signal WT_INT to generate a second monitor signal MS 2  when the monitor enable signal M_EN is enabled. The second output unit  26  may selectively output the second internal output data RDATA 2  and FDATA 2  or the second monitor signal MS 2  as a second output data DOUT 2  in response to the monitor enable signal M_EN. The second output data DOUT 2  may be supplied through the second pad  21 . The second output unit  26  may output the second monitor signal MS 2  as the second output data DOUT 2  when the monitor enable signal M_EN is enabled. The second output unit  26  may output the second internal output data RDATA 2  and FDATA 2  as the second output data DOUT 2  in synchronization with the internal clock signals RCLK and FCLK when the monitor enable signal M_EN is disabled. 
       FIG. 2  is a circuit diagram of an example of first monitor signal generator  15  of the semiconductor memory device of  FIG. 1 .  FIG. 3  is a circuit diagram of an example of first output unit  16  of the semiconductor memory device of  FIG. 1 . 
     As illustrated in  FIG. 2 , the first monitor signal generator  15  may be configured to have a NAND gate ND 11 . The NAND gate ND 11  may receive the monitor enable signal M_EN and the read internal signal RD_INT as two input signals thereof and may generate the first monitor signal MS 1  as an output signal thereof. When the monitor enable signal M_EN is enabled to have a logic “high” level, the first monitor signal generator  15  may inversely buffer the read internal signal RD_INT and may output the inversely buffered read internal signal RD_INT as the first monitor signal MS 1 . The second monitor signal generator  25  may have the same or similar configuration as the first monitor signal generator  15 . That is, the second monitor signal generator  25  may also be configured to have a NAND gate, and the NAND gate may receive the monitor enable signal M_EN and the write internal signal WT_INT as two input signals thereof and may generate the second monitor signal MS 2  as an output signal thereof. 
     As illustrated in  FIG. 3 , the first output unit  16  may be configured to include an internal data transmitter  161 , a monitor signal transmitter  162 , a latch unit  163  and an output driver  164 . The internal data transmitter  161  may inversely buffer the first internal output data RDATA 1  and FDATA 1  and may transmit the inversely buffered first internal output data RDATA 1  and FDATA 1  to an internal node ND 11  in synchronization with the internal clock signals RCLK and FCLK when the monitor enable signal M_EN is disabled to have a logic “low” level. The monitor signal transmitter  162  may inversely buffer the first monitor signal MS 1  and may transmit the inversely buffered first monitor signal MS 1  to the internal node ND 11  when the monitor enable signal M_EN is enabled to have a logic “high” level. The latch unit  163  may latch a signal on the internal node ND 11  and may buffer and output the latched signal. The output driver  164  may generate the first output data DOUT 1  in response to the output signal of the latch unit  163 . The second output unit  26  may have substantially the same configuration as the first output unit  16 . In other words, the second output unit  26  may have the same circuit as the first output unit  16 . The only difference between the first and second output units  16  and  26  is that I/O signals of the first output unit  16  are different from I/O signals of the second output unit  26 . 
     Hereinafter, a monitoring operation of the semiconductor memory device described above will be developed. The monitoring operation may include a first monitoring operation which is executed when the first data I/O block  1  operates in a write mode and a second monitoring operation which is executed when the second data I/O block  2  operates in a read mode. 
     First, when the first data I/O block  1  operates in a write mode, the second monitor signal generator  25  may buffer the write internal signal WT_INT generated by the first write path unit  13  to generate the second monitor signal MS 2  if the monitor enable signal M_EN is enabled. The second output unit  26  may buffer the second monitor signal MS 2  and may transmit the buffered second monitor signal MS 2  to the second pad  21 . 
     Next, when the second data I/O block  2  operates in a read mode, the first monitor signal generator  15  may buffer the read internal signal RD_INT generated by the second read path unit  24  to generate the first monitor signal MS 1  if the monitor enable signal M_EN is enabled. The first output unit  16  may buffer the first monitor signal MS 1  and may transmit the buffered first monitor signal MS 1  to the first pad  11 . 
     As described above, the write internal signal WT_INT generated when the first data I/O block  1  operates in a write mode may be verified through the second pad  21 . Hence, a write operation of the first data I/O block  1  can be monitored by reading out the write internal signal WT_INT through the second data I/O block  2  which is separated from the first data I/O block  1 . Thus, a design margin relating to the write internal signal WT_INT may be verified by the monitoring operation, and failure analysis of the semiconductor memory device may be more readily performed. Further, the read internal signal RD_INT generated when the second data I/O block  2  operates in a read mode may be verified through the first pad  11 . Hence, a read operation of the second data I/O block  2  can be monitored by reading out the read internal signal RD_INT through the first data I/O block  1  which is separated from the second data I/O block  2 . Thus, a design margin relating to the read internal signal RD_INT may be verified by the monitoring operation, and failure analysis of the semiconductor memory device may be more readily performed. 
       FIG. 4  is a block diagram of a semiconductor memory device  200  according to another embodiment. 
     As illustrated in  FIG. 4 , semiconductor memory device  200  according to the present embodiment may be configured to include a data input block  3  and a data I/O block  4 . The data input block  3  may be configured to include a first pad  31 , a first input buffer  32  and a first write path unit  33 . The data I/O block  4  may be configured to include a second pad  41 , a second input buffer  42 , a second write path unit  43 , a read path unit  44 , a monitor signal generator  45  and an output unit  46 . 
     The first input buffer  32  may buffer a first input data DIN 1  supplied through the first pad  31  to generate a first internal input data INT_DIN 1  when the data input block  3  operates in a write mode. The first write path unit  33  may drive a first global I/O line to transmit the first internal input data INT_DIN 1  to the first global I/O line GIO 1  when the data input block  3  operates in the write mode. The first write path unit  33  may also generate and output a write internal signal WT_INT when the first internal input data INT_DIN 1  is transmitted to the first global I/O line GIO 1 . 
     The second input buffer  42  may buffer a second input data DIN 2  supplied through the second pad  41  to generate a second internal input data INT_DIN 2  when the data I/O block  4  operates in a write mode. The second input buffer  42  may interrupt buffering the second input data DIN 2  in response to a buffer off signal BOFF when a monitor enable signal M_EN is enabled. The second write path unit  43  may transmit the second internal input data INT_DIN 2  to a second global I/O line GIO 2  when the data I/O block  4  operates in the write mode. The read path unit  44  may receive internal output data INT_DOUT from data loaded on the second global I/O line GIO 2  when the data I/O block  4  operates in a read mode. The monitor signal generator  45  may buffer the write internal signal WT_INT to generate a monitor signal MS when the monitor enable signal M_EN is enabled. The monitor signal generator  45  may also generate the buffer off signal BOFF for interrupting the operation of the second input buffer  42  when the monitor enable signal M_EN is enabled. The output unit  46  may selectively output the internal output data INT_DOUT or the monitor signal MS as an output data DOUT in response to the monitor enable signal M_EN. The output data DOUT may be supplied through the second pad  41 . The output unit  26  may output the monitor signal MS as the output data DOUT when the monitor enable signal M_EN is enabled. Alternatively, the output unit  26  may output the internal output data INT_DOUT as the output data DOUT when the monitor enable signal M_EN is disabled. As described above, the write internal signal WT_INT generated when the data input block  3  operates in a write mode may be verified through the second pad  41 . Hence, a write operation of the first data input block  3  can be monitored by reading out the write internal signal WT_INT through the data I/O block  4  which is separated from the data input block  3 . Thus, a design margin relating to the write internal signal WT_INT may be verified by the monitoring operation, and failure analysis of the semiconductor memory device may be more readily performed. Further, the operation of the second input buffer  42  may be interrupted when the write internal signal WT_INT is monitored. This is for preventing the write internal signal WT_INT from being disrupted by the operation of the second input buffer  42  when the write internal signal WT_INT is monitored through the second pad  41 . 
       FIG. 5  is a block diagram illustrating a configuration of a semiconductor memory device  300  according to yet another embodiment. 
     As illustrated in  FIG. 5 , semiconductor memory device  300  may be configured to include a first data input block  5 , a second data input block  6  and a data I/O block  7 . The first data input block  5  may be configured to include a first pad  51 , a first input buffer  52  and a first write path unit  53 . The second data input block  6  may be configured to include a second pad  61 , a second input buffer  62  and a second write path unit  63 . The data I/O block  7  may be configured to include a third pad  71 , a third input buffer  72 , a selection input unit  73 , a third write path unit  74 , a read path unit  75 , a monitor signal generator  76  and an output unit  77 . 
     The first input buffer  52  may buffer a first input data DIN 1  supplied through the first pad  51  to generate a first internal input data INT_DIN 1  when the first data input block  5  operates in a write mode. The first write path unit  53  may drive a first global I/O line GIO 1  to transmit the first internal input data INT_DIN 1  to the first global I/O line GIO 1  when the first data input block  5  operates in the write mode. The first write path unit  53  may also generate and output a write internal signal WT_INT when the first internal input data INT_DIN 1  is transmitted to the first global I/O line GIO 1 . 
     The second input buffer  62  may buffer a second input data DIN 2  supplied through the second pad  61  to generate a second internal input data INT_DIN 2  when the second data input block  6  operates in a write mode. The second write path unit  63  may transmit the second internal input data INT_DIN 2  to a second global I/O line GIO 2  when the second data input block  6  operates in the write mode. 
     The third input buffer  72  may buffer a third input data DIN 3  supplied through the third pad  71  to generate a third internal input data INT_DIN 3  when the data I/O block  7  operates in a write mode. The third input buffer  72  may interrupt buffering the third input data DIN 3  in response to a buffer off signal BOFF when a monitor enable signal M_EN is enabled. The selection input unit  73  may selectively output the second internal input data INT_DIN 2  or the third internal input data INT_DIN 3  as a selection input data DIN_SEL in response to the monitor enable signal M_EN. The third write path unit  74  may transmit the selection input data DIN_SEL to a third global I/O line GIO 3  when the data I/O block  7  operates in the write mode. The read path unit  75  may receive internal output data INT_DOUT from data loaded on the third global I/O line GI 03  when the data I/O block  7  operates in a read mode. The monitor signal generator  76  may buffer the write internal signal WT_INT to generate a monitor signal MS when the monitor enable signal M_EN is enabled. The monitor signal generator  76  may also generate the buffer off signal BOFF for interrupting the operation of the third input buffer  72  when the monitor enable signal M_EN is enabled. The output unit  77  may selectively output the internal output data INT_DOUT or the monitor signal MS as an output data DOUT in response to the monitor enable signal M_EN. The output data DOUT may be supplied through the third pad  71 . The output unit  77  may output the monitor signal MS as the output data DOUT when the monitor enable signal M_EN is enabled. Alternatively, the output unit  77  may output the internal output data INT_DOUT as the output data DOUT when the monitor enable signal M_EN is disabled. 
       FIG. 6  is a circuit diagram illustrating an example of a selection input unit included in the semiconductor memory device  300  of  FIG. 5 . 
     As illustrated in  FIG. 6 , the selection input unit  73  may be configured to include a transfer gate T 71  supplying the second internal input data INT_DIN 2  as the selection input data DIN_SEL when the monitor enable signal M_EN is enabled to have a logic “high” level, and a transfer gate T 72  supplying the third internal input data INT_DIN 3  as the selection input data DIN_SEL when the monitor enable signal M_EN is disabled to have a logic “low” level. 
     As described above, the write internal signal WT_INT generated when the first data input block  5  operates in a write mode may be verified through the third pad  71 . That is, a write operation of the first data input block  5  can be monitored by reading out the write internal signal WT_INT through the data I/O block  7  which is separated from the first data input block  5 . Thus, a design margin relating to the write internal signal WT_INT may be verified by the monitoring operation, and failure of the semiconductor memory device  300  may be more readily performed. Further, the operation of the third input buffer  72  may be interrupted when the write internal signal WT_INT is monitored. This is for preventing the write internal signal WT_INT from being disrupted by the operation of the third input buffer  72  when the write internal signal WT_INT is monitored through the third pad  71 . Moreover, according to the present embodiment, a write operation may be executed by the second internal input data INT_DIN 2  transmitted to the selection input unit  73  even when the write internal signal WT_INT is monitored through the third pad  71 . Therefore, even when the data I/O block  7  receives data from the second data input block  6  to execute a write operation for transmitting the data to the third global I/O line GIO 3 , a write operation of the first data input unit  5  may be monitored. Thus, an additional and special time may not be required to monitor the write operation of the first data input unit  5 . 
     The example embodiments of the inventive concept have been disclosed above for illustrative purposes. Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the inventive concept as disclosed in the accompanying claims.
A semiconductor memory device includes, in part, a first data I/O block and a second data I/O block. During a write operation, the first data I/O block transmits input data supplied through a first pad to a first global I/O line, and further generates a write internal signal. The second data I/O block transmits the write internal signal to a second pad in response to a monitor enable signal. During a read operation, the first data I/O block supplies data from the first global I/O line to a first pad, and further generates a read internal signal. The second data I/O block transmits the read internal signal to the second pad in response to a monitor enable signal.