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T Modules

T(lights & switches). T(lights & switches) is an interface between an RTM system and the human user. It has a set of 16 toggle switches which may be set manually, and read by the Bus, i.e. <- switches<15:0>. In addition, there are 4 auxiliary toggle switches. (S1, S2, S3, and S4). These switches are wired single- pole-double-throw to ground, and are expressly intended to provide the Bus control switches for Kbus. However, with suitable adaptations they can be used in K(manual evoke)'s and as Boolean conditions. This module also has 20 display lights. Sixteen of these can be read from the Bus, i.e., Lights<15:0> <-. Of the other four, two correspond to the Bus timing signals, DA and DR, and the other two, L1 and L2, can be used to display Boolean data. If the Monitor enable input is grounded, then all Bus transfers will appear on the lights.

T(serial interface). This module is used as an interface to a standard Teletype, model 33, 35, or 37, either ASR or KSR, operating as either half duplex or full duplex. There are two registers, Transmit \T and Receive \R, which buffer the output to, and input from the Teletype, respectively.

If it is desired to receive a character from the Teletype papertape reader, the Start R operation is evoked. When the character has been received by the R register, Rflag goes to a 1. Then the character can be read onto the Bus, and Rflag cleared by a single evoke operation (i.e. <- R; Rflag <- 0). If another character is written into the R register before it is read, the Overun flag goes to a 1.

To send a character to the Teletype, one must first monitor the Tflag. If it is a 1, the Teletype is ready to receive a character. Then one can send the character and clear the Tflag with a single evoke-operation (i.e. T <-; Tflag <- 0).

Since Start R is an operation that does not require the Bus, it may be evoked in parallel with some other operation that does. If so, the Boolean DA disable input must be set to 0, as in the DMflag and the Mtr described previously.

T(analog-to-digital converter)\Tad. Tad converts an analog input into digital form for entry into the RTM system. It contains a register, a-d<9:0>, which contains the digital value which is proportional to the analog input. Since it takes time to do an a-d conversion, the control may be operated in either of two ways. In the first way, the user may evoke the operation <- a-d<9:0>,and the conversion will be made, then the result read onto the Bus, all the time holding up control flow. In the second way, a command to initiate a conversion may be given (Start a-d), and then after the a-d flag signals that the conversion is complete (by going to 1), the <- a-d<9:0> operation is evoked. In the latter mode, the Bus may be used for other purposes while the conversion is going on. The <- a-d<9:0> operation also clears the a-d flag. Since this is not yet a standard PDP-16 module, it needs some additional steering logic to make it compatible. Thus, the, user may implement the DA generation scheme for the Start a-d signal as he sees fit. The alternatives are: (1) generate a DA whenever Start a-d is evoked; (2) alternative (1) coupled with an optional DA disable input; (3) no DA generated by Start a-d, so it must always be evoked in parallel with some DA generating operation. Similarly, a DR generation circuit must accompany <-a-d. Chapter 7 shows standard formats for DA and DR signal generation.

T(digital-to-analog)\Tda. The Tda contains a register, d-a, which when loaded forms an analog voltage proportional to the value in the register. The output analog signal is continuous. Thus the only functional command for the module is d-a <-. Here, as in the case of Tad, it is up to the user to provide a DA generation circuit.


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