Solartron Mobrey 3595 4C, User Manual

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3595 4C User Manual Part One Programming the 3595 4C Interface card
35952350 (CH03/AA)
3-11
3.4.5 Real-time calendar and clock
The 4C Interface card maintains a real-time calendar and clock (Figure 3.3) for timing and the IMP functions.
Calendar Synchronise
0xEE
0xEF
0xF0
0xF1
0xF2
0xF3
0xF4
Bit 7 Bit 0
CGT CIE CRQ
Year
Month
Day
Hour
Minutes
Seconds
Millisecs (100's) Millisecs (10's)
Millisecs (1's)
0xF5
0cF6
0xF7
Calendar Set
Real-time
Calendar
and Clock
Figure 3.3: Real-time calendar and clock
The on-card calendar and clock are set by the Host PC and can be left to run with an accuracy determined
by the on-card crystal (error less than 2.5 seconds a day). Alternatively, it is possible to synchronise the 4C
Interface card clock to the Host PC clock. Access to the on-card calendar and clock is requested by the
PC, and granted by the card, through the Calendar Set Register. The on-card calendar and clock are set
by writing an eight-byte time value into locations 0xF0 through 0xF7. Each byte is expressed in the binary-
coded decimal format. Synchronisation to the Host PC clock is maintained through the Calendar
Synchronise Register.
Synchronising the clock
If software synchronisation is to be used for the real-time clock, the byte at location 0xEE should be set
non-zero on the second boundary. The 4C Interface card clears this byte ready for the next
synchronisation.
Accessing the calendar
Access to the real-time calendar by the Host PC is requested and granted through the Calendar Set
Register, at location 0xEF. The bit functions of this register are as follows:
CGT Bit 7: Calendar Grant. The ‘1’ state indicates to the Host PC that access to the calendar is
granted
CIE Bit 6: Calendar Interrupt Enable. When set to ‘1’, causes Host PC to be interrupted when
calendar access is granted.
CRQ Bit 0: Calendar Request. When set to ‘1’, requests access to the calendar by the PC
Setting up the calendar and clock
To set-up the real-time calendar and clock, the procedure is as follows:
1.
Request access to the calendar and clock by setting the Calendar Request bit (CRQ) in the Calendar
Set Register. In addition, set the Interrupt Enable bit (CIE) if an interrupt is required when access is
granted.