Remote Technologies RPC-320 manual Programming, Gnd, Load, Gate, Program examples

MULTI-MODE COUNTER

DESCRIPTION

The 24 bit multimode counter is capable of up/down, binary, divide-by-n, and quadrature inputs. C ount frequency is DC to 20 M hz. The R PC-320 uses an LSI Com puter Syste ms LS 7166. Its data sheet is foun d in Appendix C.

The COU NT function and statement are used to read from and wr ite to the counter . L INE B is used to program the chip for various op erating mode s.

An interrupt, using ONITR, may be detected on a carry, borr ow, or either event. The eve nt is jumper selectable through W8. When the counter is used, external interrupts (see Chapter 12) may not be used.

W8 P in	Description
1-2	External TTL level through P2-6 or
	optically isolated through P3
3-4	Carry or borrow pulse from counter
5-6	Carry pulse from counter
7-8	Borrow pulse from counter

Signals connect to the counter via P2. Use the following table to determine signal input to the LS7166.

P2	Function
Name
A IN	Count inp ut A
B IN	Count inp ut B
GND	Ground
LOAD	Load counter/latch (LCTR/LLTC)
GATE	Gate/reset counter (ABGT/RCTR)

Input lines (A IN), (B IN), LOAD, and GATE are pulled to + 5V through a 10K resistor .

PROGRAMMING

The LS7166 is capable of several operating modes, all of which are not discussed here. See Appendix C for this chips operating modes. W hat are shown are exam ples of how to program this chip.

NOTE: Be sure to initialize the counter chip before using COU NT com mands. Failure to do so returns m eaningless results.

The COU NT function returns the current counter value.

SECTION 13

Specifically, RPBASIC w rites a 2 to the MCR (M aster Control Register), reads the 3 counter bytes from the OL (Output latch), and converts it to the proper internal BASIC form at.

100 A = COUNT(0)

COUNT statement writes a 24 bit number to the PR (Preset r egister) only. Its syntax is:

200 COU NT 0, D

To transfer this number to the counter, execute the following in the program:

LINEB 6,1,8

The counter number is always 0 on the RPC -320.

LINEB is used to access specific registers within the chip. Accessing control and status registers is shown below. C ounter bank is 6.

100A = LINEB(6,1) : REM Read OSR

200LINEB6,1,X

Line 200 writes to OCCR, ICR, QR, MCR, and ICR register s. W hich registe r selected is determ ined by bits 6 and 7 in the byte written to the chip.

Program examples

This code resets the counter and enables the inputs. The count is printed once a second. To see the count change, momentarily bring " A IN" or "B IN" on P2 to ground.

When " B IN" is gr ounded, the count decrem ents.

10LINEB6,1,32

20LINEB6,1,64+8

30ONTICK 1,500

40GOTO 40

500PRINT COUNT(0)

510RETI

Line 20 can be shortened somewhat . 64 selects the ICR (Input contr ol register ) and 8 enab les inputs. 72 could have been used.

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