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Application Note

New PMAC Communication Variables - 7167 New PMAC Communication Variables in Firmware 1.16F or Newer

Firmware version V1.16F for the (non-Turbo) PMAC and PMAC2 introduced two new I-Variables to improve the efficiency and robustness of communications with the host computer. Used properly, these variables significantly speed up communications and help robustness, in a backward-compatible manner. However, if the user executes a certain sequence of events, he may inadvertently foul up existing communications routines.

I63 Control-X Echo Enable

New variable I63, when set to 1, causes PMAC to respond to a clear-communications-buffers command with another when the buffers have been cleared. This means that the host computer does not have to wait for a safe timeout period before sending the next command, greatly improving the speed of robust communications routines in multi-tasking systems, such as the “Pmac_get_response” procedure in the PCOMM32 Windows library. If I63 is set to 0, PMAC does not create any response to a command, making the operation backward compatible with older firmware versions, which never created any response to .

I64 Internal Response Tag Enable

New variable I64, when set to 1, causes PMAC to start an unsolicited message to the host (one in response to an internal CMD or SEND statement) with a character. This allows the host to distinguish it easily from an expected solicited response to a host command. If I64 is set to 0, PMAC does not add a character to the beginning of an unsolicited message, making the operation backward compatible with older firmware versions, which never added the character.

The PEWIN Communication Process

New versions of the PEWIN32 Executive programs (V2.32 and higher, released after V1.16F firmware) by default set I63 and I64 to 1 to speed communications and to reliably place unsolicited communications in the terminal window. If one of these revisions of PEWIN32 is used with default settings, forcing I63 and I64 to 1, and then communications is attempted with routines that cannot handle these new settings, that communications will likely fail. Note that in battery-backed versions of PMAC(1) with V1.16F and G firmware, I63 and I64 values are maintained by the battery, so new values will be retained even without a SAVE command. With V1.16H and newer firmware for battery-backed PMAC(1) boards, these values are maintained in the EEPROM memory, so new values of I63 and I64 must be stored with a SAVE command to be retained through a power-cycle or reset. On flash-backed PMAC(1) boards (PMAC1.5) and all PMAC2 boards, new values of I63 and I64 will not be retained through a power cycle or board reset unless they have been stored with a SAVE command. Delta Tau’s PCOMM32 communications libraries V10.32 and higher (which are required with the newer PEWIN32 versions) can handle communications properly regardless of the settings of I63 and I64 – although communications will be more efficient with these variables set to 1. However, older versions of the library, and user-written communications routines without knowledge of these new features, may have trouble communicating with the card if these variables are set to 1.
New PMAC Communication Variables in Firmware 1.16F or Newer 1