Channel command words

Table 1 contains the channel commands used by VTAM® to send data to and receive data from channel-attached non-SNA 3270 terminals.

Table 1. Channel command words for channel-attached non-SNA 3270 devices
Command code (hex)	Command	Description
01	Write	Transfers data from storage in the host processor to the I/O device. Modifies existing buffer data.
02	Read or Read buffer	Transfers the entire buffer contents from the I/O device to storage in the host processor.
05	Erase/Write	Clears the device buffer before starting the write.
06	Read Modified	Transfers data (that was modified since the last read) from the I/O device to storage in the host processor.
0B	Select	Transfers data from the I/O device buffer to the controller buffer. Separates the device-to-controller unit buffer transfer from the execution command.
0D	erase/write Alternate	Same as Erase/Write, except that it allows for a larger buffer size required for some devices.
1B	Select Read Buffer	Same as Select, except that it is used only for Read buffer channel programs.
4B	Select Write	Same as Select, except that it is used only for Write channel programs.
0F	Erase All Unprotected	Clears all unprotected buffers
11	Write Structured Field	Writes a structured field