Using the 93LC56 and 93LC66
16c5x/7x Cross-Assembler V4.12 Released
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LIST P=16C54,c=132
;****************************************************************
;
3-Wire Byte Write with Data Poll Program (107 bytes)
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This program demonstrates how to interface a
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Microchip PIC16C54 to a 93LC56 or 93LC66 Serial EE
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device. This program will execute the erase/write enable
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command, write to 8 consecutive addresses, and then
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use the ‘data polling’ method to determine when the
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write cycle is complete. The program then executes
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the erase/write disable command. This sequence will
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repeat forever.
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When writing to a 3-wire serial EE device, the
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internally timed write cycle will begin after
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the opcode, address and data are sent to the
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device. There are two ways to make sure that the
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cycle is complete before you send it another command.
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The simplest method is to simply wait for the maximum
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write cycle time, which can be obtained from the data book.
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A more efficient method is “Data polling.” This is
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done by toggling the chip select line low and then
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back high after the opcode, address and data are sent.
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The chip select line must be low for at least 250ns
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before bringing it high again. The device will pull
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the data out line low at that point, and set it high
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when the write cycle is complete. The user can then check
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or “poll” the dataout line until it goes high before
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sending the next command.
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As an option, the user can connect a LED to pin 18
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on the PIC16C54 (use about a 1K resistor in series) as a
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timeout indicator. This LED will come on if the
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data polling is unsuccessful and the device being
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programmed does not respond. This can be tested by
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simply running the program with no part in the socket.
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This program communicates to the serial EE in the
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x16 mode, and ASSUMES THE USER HAS SET THE ORG PIN
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ON THE DEVICE TO Vcc.
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Timing is based on using the PIC16C54 in ‘XT’ mode
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using a 4Mhz crystal. Clock speeds to the serial EE
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will be approximately 50 kHz for this setup.
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PIC16C54 to Serial EE Connections:
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PIC16C54
Serial EE
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——————
——————
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Pin 10 (RB4) —> Chip Select
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Pin 11 (RB5) —> Clock
Mon Jun 06 10:49:00 1994
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Mon Jun 06 10:49:00 1994
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16c5x/7x Cross-Assembler V4.12 Released
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Pin 12 (RB6) —> Data In
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Pin 13 (RB7) —> Data Out
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ORG=Vcc
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;************************************************************
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Register Assignments
;************************************************************
port_a equ
5h
; port 5 (port_a)
port_b equ
6h
; port 6 (port b) used comm lines to serial EE
© 1994 Microchip Technology Inc.
DS00560D-page 11
8-109
MICROCHIP [ MICROCHIP TECHNOLOGY ]
