Fabrice Courtois

Major Typo Error?

Discussion created by Fabrice Courtois on Nov 21, 2006
Latest reply on Jan 20, 2007 by Jeff Smith
Reading page 14 of AN2287:
 
Multiplexed Data Bus (PORTA and PORTB)
Internally HCS12 Family devices have full 16-bit data paths. But, depending
upon the operating mode, the external data bus may be 8 or 16 bits.
In external wide modes, the 16-bit data bus is made up of ports A and B.
• Bidirectional PORTB[7:0] shares functionality with the low byte of the
data bus DATA[7:0] and low byte of the address bus
• Bidirectional PORTA[7:0] shares functionality with the high byte of the
data bus DATA[15:8] and high byte of the address bus
In external narrow modes, the 8-bit data bus is made up of port A only.
• Bidirectional PORTA[7:0] shares functionality with the low byte of the
data bus DATA[7:0] and high byte of the address bus
• Data accesses are split into two consecutive 8-bit accesses so only port
A is used as the data bus. In this case, the external data bus does two
consecutive 8-bit accesses to handle 16-bit data requests from the
MCU.
NOTE: Back-to-back writes will not negate the R/W signal.
 
That should be a mistake in that the low byte of the data bus is shared with the low byte of the address bus,  not the high byte.
 
If the statement in the application note is true and all other references in all the other documentation from Fresscale, specifically on pinout diagrams, are false, that explain why my board will not start.
 
Fabrico

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