Apple 1 Cassette Interface

APPLE-l CASSETTE INTERFACE INTRODUCTION The Apple Cassette Interface (ACI) is a peripheral device for the Apple Computer which enables the user to store and retrieve information (data and programs) using a standard audio grade cassette recorder. The ACI attaches directly to the Apple Computer and jacks are provided on the ACI board to connect to the cassette recorder. The ACI reads and writes data at the rate of approximately 1500 baud (depending upon the data). All the ACI timing is done in software, resulting in extreme accuracy, no adjustments, and consistency between units. resulting in the inability to accurately read a tape that has been recorded on a different machine. However, if the same unit is used for both recording and reading, even the cheapest of cassette recorders will work reliably. Most tapes available in the $2-$4 category work well for data storage. You may experience an occasional tape which 'loses bits,' which is caused by severe oxide thickness variations on the tape and cannot be corrected. Special leaderless tapes need not be used as the ACI automatically transmits a ten second 'header' of all ones before transmitting the data, which insures that the leader will have passed. T APE RECORDERS & TAPE JUMPERS Almost any cassette recorder will work well with the ACI. As a recommendation, we have found the least expensive (under $40) Panasonic to be very reliable and of good quality, although it is not equipped with a tape counter, which is useful (though not essential) for locating files within a tape. (An alternative method of discerning files is to record a voice identification between files. ) Among the 'under $25' cassette recorders there may be variations in head alignment and internal electronics, For operation of the ACI, a permanent jumper must be placed between 'R' and 'C' in the block select area of the main board (B9,10). This jumper from 'R,' which is connected to enable the ACI, to 'C' selects the ACI when the 12th 4K block eC') is addressed. Also, for running Apple Basic in the 2nd 4K bank of on-board memory, it is necessary to break the solder jumper between 'w' and '1' and then jumper 'w' to 'E.' This moves the 2nd 4K bank from the 'I' block to the 'E' block, which is where Apple Basic resides. INST ALLATION Install the ACI board into the connector on the main board with the components on the ACI board facing away from the main board (the jacks to the edge of the main board). SEE FIGURE 1. The system power should be OFF whenever installing or removing the ACI board. Install cables from the ACI jack marked "TO TAPE" to the recorder microphone input and from the ACI jack marked "FROM TAPE" to the recorder earphone output. One cable can be appropriately switched between the two paths if necessary. INSTALLATION DIAGRAM USING THE ACI The Cassette program is contained in two PROMS on the ACI board and runs at ClO~. When entered, the program should echo an "*." The format for specifying the memory address ra…