In 7525 Compatibility Mode, the 7526 DCT will not generate DI&mdash.initiated transactions, or show that there is more than 32Kb of RAM installed. It will, however, use all of the RAM that is installed for files and transaction storage if so configured.
In the enhanced mode, data sent or the response from the DCT is changed for the following commands:
The primary differences between Enhanced Mode and 7525 Compatibility Mode are that the format of the transactions generated by the 7526 DCT, and the format of the responses to the commands listed above are changed. The 7526 DCT will understand commands sent in either format, regardless of the mode specified. It will also allow all functions (except DI&mdash.initiated transactions) in 7525 Compatibility Mode.
The asynchronous serial protocol and command set used by the 7526 DCT is compatible with the 7527 DCT, allowing both types of terminals to be used on a common communications line. The 7526 DCT uses lowercase a-y, 0-6 addressing, while the 7527 DCT uses uppercase A-Y, 0-6 addressing, to preclude conflicts except in the 0-6 range. There can be only one of 0-6 addresses on the same line. The 7525 terminals can also be on this line, however, addresses a-p will conflict with the 7526 DCT.
The following table depicts the addressing overlap among the DCTs.
Table 1. Addressing Overlap
+------------------+------------------+------------------+------------------+ | A-Y | 0-6 | a-p | q-y | +------------------+------------------+------------------+------------------+ | 7527 | 7527 | 7525 | | +------------------+------------------+------------------+------------------+ | | 7526 | 7526 | 7526 | +------------------+------------------+------------------+------------------+Refer to Appendix E. "Comparisons Between IBM 7525 and 7526 DCT Operations" for operational differences.
The 7526 DCT microcode provides a set of functions and device drivers including real-time clock, timers, display, keypad, communications port, DI/DO (Digital Input/Digital Output) port; and bar code and magnetic decoding.
The 7526 DCT is software compatible with the 7525 DCT and provides additional features made possible through additional ROM space, new hardware design and RAM expandability up to 256Kb.
The 7526 DCT keypads are shown in Figure 1. and Figure 2..
(3) Throughout this document, CMD represents command. For example, CMD A means Command A. The meanings of CMD P and all other communications commands are explained in Chapter 6. "Communications Control Commands".