Micro­power

then immediately accessed as described below. At the end of each routine a suitable message is output, either confirming the completion, or indicating that errors have occurred. This message is held on the screen for approximately 2 seconds, and then the program jumps back to the label ‘RESTRT’, and the user is asked if he wants to carry on with the same type of chip. A response of ‘Y’ will take him back to the menu, while ‘N’ will return him to the key ‘C’/warning mesage routine, followed by chip type selection.

The Routines

E – Check For Erased EPROM

This routine needs no further information from the user and it immediately reads each byte in succession from the chip, checking that its value is 0FFH. If all the bytes are FF, the routine ends with a message saying that the EPROM is erased. If any byte is detected which is not FF, the routine terminates immediately and the message “EPROM” not fully erased” appears. The operation of the routine is very rapid.

The remaining four routines all need a four digit hexadecimal address in order to continue. A subroutine is called when the program enters the chosen routine; this subroutine prompts the operator to enter the required address. It checks the data as it is entered, and only allows valid hexadecimal digits to be stored. If an error is made during the entry of the four digits, the user must continue until four entries have been made. He will then be given a chance to change the whole entry. On exit from the subroutine, the addres will be in the HL register pair, and also in the workspace at label STOR1.

The address entered will be used as the start of a 1K or 2K block of RAM in the computers memory by the program, transfer and compare routines; for the ‘Dump’ routine, the normal operating address of the chip should be entered. This address will be printed at the start of each line of data, incrementing by 10H for each line.

P – Program EPROM From Data In RAM

After obtaining the address to be used as the start of the data to be put in EPROM and setting up the counters, etc., the routine tests the value at ROMFLG to decide whether 1K or 2K chips are to be programmed. Depending on this value, it selects the appropriate programming routine; two separate routines are required because the programming requirements of the two types of chip are very different. 2708s need each address to be cycled a large number of times (100 – 1000) with a programming pulse of between .1 and 1 millisecond., to produce a total ‘burn’ time of 100 milliseconds per address. 2516/2716 chips need only one cycle, with a