Dynamic Shift Registers - Bitsavers - Trailing-Edge

enECD;>en"0~cao.c>CD~CCD(,)...ca~CD...CPinTimingKeyboardArithmetic RegisterControl&InterfaceUnit UnitROMControlChip(AU) (RU) (CRaM)(T&C)(KIIMM5700 MM5701MM5703MM5702 MM57 041 RES III ALOUf2 t/l2 CM CS3 RES 102 fE t/l2 R74 102 pi R65 101 101 CM R56 pi t/ll t/ll R47 t/ll Pl R38 Vss Vss P2 Vss R29 CM t/l2 t/ll Idle Key Reset10 TE TE Rl11 P02 t/l2 RO12 POl CM Vss Vss13 Pm! FFO t/ll14 P04 RES t/l215 pi CM16 VGG VGG VGG T417 10 T118 T219 OS T320 B+9 T521 pi22 BUSl23 A BUS224 VGG VGGFIGURE 1. MAPS Pin AssignmentsNInIZ4WHAT IT DOESIn addition to the 32 character key switch closuresthat may be encoded, there are 8 static switchesthat may be interrogated. These static switchesmay be controlled by the user to form an 8-bitword which upon command will be sent via thekeyboard interface output to· the rest of the system.These switch closures are used to performcontrol functions. They may be used to form anydesired data word especially if it is to be variedfrom time to time.The output of this device is presented at Pin 2' ina bit serial fashion. This organization was requiredto be compatible with the bus structured organizationof the five chip MAPS. The bit serial, digitserial, organization of this system was designedto keep to a minimum the number of pins requiredfor each MOS-LSI chip used in this system. Actually,Pin 2' is a bidirectional bus, with inputcapability for controlling static switch interrogation,data interrogation, or control of the alarmand shift functions. In a system this is accomplishedwith time mUltiplexing. (Figure 5)If a system contains more than 32 character keyclosures, the functions performed by the MM5704may be expanded by paralleling two or more ofthese devices. Two devices will provide 64 keyclosures ('28 data words), three provide 96, etc.The two key rollover and three key alarm functionswill continue to function by paralleling the busy'(Pin 22) and busy 2 (Pin 23) signal lines. Thealarm signal will be available at Pin , of thedevices. This signal is not OR-tieable.TWO KEY ROLLOVERIf a second key is depressed before the first keyis released, a condition exists that is defined as twokey rollover. In this situation, the device will acknowledgeand transmit the encoded word generatedby the initial key closure then acknowledgeand transmit the encoded data word generated bythe second key closure. At the time that the systemresponds to the initial key closure, the "busy'" signal line becomes true (MOS logic "'" condition).This informs any parallel keyboard interfacechips that a key closure has been detected. The"busy'" signal will remain true until the encodeddata word resulting from initial key closure hasbeen transmitted and the key released.If during the time that the "busy'" signal is trueand a second key closure is detected, the systemwill flag this condition by causing "busy 2" to gotrue. "Busy 2" will remain true until the encodeddata word generated by the initial key closure hasbeen transmitted and one key released. "Busy'"will remain true until all keys are released. A keyonce depressed and acknowledged by the systemmust be released and depressed again before it willbe accepted and acknowledged as valid by thesystem for the second time.THREE KEY ALARMIf three or more keys are depressed, a conditionexists that will be detected by the system andinterpreted as the alarm condition. Because theKI chip cannot process more than two key closures,depression of more than two must alarmthe system. When the alarm condition exists, a252