D) The PROM Read Data bus returns the 8-bit data word in the selected PROM location to the Control Board.
There are six major components of the UPP-878 Personality Card as shown in Figure 4-1:
1) The PROM address logic examines the l2-bit address from the Control Board. A bank of switches (Sl) is incor-porated in the PROM address logic. The state of these switches should reflect: the type of PROM (2708 or
2704) being programmed. See Figure 4-2 for the location and switch settings of Sl. The PROM Programmer operator may change the setting of Sl if necessary. (Refer to Section 7.2 for instructions for the removal and
installation of Personality Cards.) Based on the state of Sl the PROM Address logic can determine if the l2-bit address exceeds the bounds of the selected PROM. If i t does, the logic will activate the address out of bounds line (AOOB/) to port 1 of a 4001 ROM (All).
2) The two Intel@400l ROMs. are a part of the MCST.:..M40 (the processor itself is located on the Control Board). The ROMs contain instructions for the MCg~~O that will effect the reading or programming of a 2708 PROM. The MC~~~O interacts with the Personality Card through the I/O ports on the two ROM chips.
3) The Voltage Regulators supply the operating voltages +12V, +26V and -SV to the PROM at VDD (pin 83), ?ROG driver (pin 82) and VBB (pin 8S), respectively. The +SV for VCC (pin 88) is supplied directly from VCCH through a dropping diode. The +26V regulator has two protective circuits. One is a current limit of 300 rnA
(set by R16 and R17) to protect the regulator and the PROG driver against shorts at the PROM socket. The
other is a crow-bar circuit that will short out the +40V supply, should the regulator fail.
--CAUTION--It is possible to damage the regulator if the personality card is removed when the +40 volt line is not totally discharged. For this reason, a user must wait 60 seconds after system power is off before removing this personality card.
4) The Write Data Gate allows the PROM Write Data from the Control Board to move on to the PROM during a program operation. The gate is closed except during a program operation. It is controlled by the Write Data Enable line from port ~ of a 4001 ROM (A5).
5) The PROM Data Logic handles the flow of data to and from the PROM. During a program operation the PROM TtVri te Data is passed on to the PROM through open collector drivers. During a read operation, the Read Data Enable line from port 3 of a 4001 ROM (All) will siq-nal the PROM Data Logic. This will allow the PROM Read Data to be passed back to the Control Board (in complemented form) .
6) The High Voltage Drivers perform the actual PROM programming. The CS/ driver is a high voltage open collector gate which when deactivated by TTCS allows CS/ to rise to programming level (12V). The program pulse (PROG) is generated by a 3-state transistor driver circuit. The PROG line (pin 82) is driven to 26V during the programming operation. During read
operations, the PROG line is grounded (see Figure 4-3).
(For compatibili ty ~Ji t.h future devices that will also
be programmed by the UPP-878 Personality Card, the "float"
during read" function can be enabled wi th the swi t.ch at 81--3. )
4-8
The remainder of this section will describe how the above function~l
blocks interact to perform the two operations: program and read.
There are two distinct locations in the ROM on the UPP-878 Personality Card that are the entry points to which the MCS~40 branches: one
entry point for a program operation and one for a read. When the Personality Card receives control i t assumes the PROM Address is available on the address bus. In the case of a program operation ilt also assumes the PROM Write Data is on the data bus. In either case the first step is to check for an address error.
The address check is a matter of "testing the Address Out Of Bounds signal (AOOB/). If the signal indicates an address error the
Personality Card aborts the opera"tion and returns control to the Control Board. If the address is valid, the operation continues.
PROM READ DATA:
In the case of a read operation there is little left that needs to be done, since the static conditions of the Personality Card pre-sent the selected PROM data word to the PROM Data Logic. All the MCS~40 needs to do is turn on the Read Data Enable line from the 4001 ROM (All) output port 3. When this is done the PROM Read Data is returned to the Control Board. The Personality Card has then completed the read operation.
PROM PROGRAM DATA:
The program operation is only slightly more involved. After the address has been checked the program operation begins. The sequenc~
of events is as follows:
1) The MCS~40 checks to see that the Voltage Regulator is receiving +40 volts from the Power Supply. If the signa~
HV Sense from the Voltage Regulator to ROM (All) port 2 is true, then the +40 volts is available. If not, the program operation is aborted, and control returns to the Con trol Board.
OFF Sl-l
~ ~ c:::JISl-2 l
JB[JSl-3 --I
~