Non-Recycle.In non-recycle count mode, the CNTR is disabled, whenever a count overflow or underflow takes place. The end of cycle is marked by the generation of a Carry (in Up Count) or a Borrow (in Down Count). The CNTR is re-enabled when a reset or load operation is performed on the CNTR.
Modulo-N.In modulo-N count mode, a count boundary is set between 0 and the content of PR. When counting up at CNTR=PR, the CNTR is reset to 0 and the up count is continued from that point. When counting down, at CNTR=0, the CNTR is loaded with the content of PR and down count is continued from that point.
The modulo-N is true bidirectional in that the divide-by-N output frequency is generated in both up and down direction of counting for same N and does not require the complement of N in the UP instance. In frequency divider application, the modulo-N output frequency can be obtained at either the Compare(FLG1) or the Borrow(FLG2) output. Modulo-N output frequency, fN=fI/(N+1) where fI is the input count frequency and N=PR.
Input/Output Control Register (Write to Control Address)
The functional modes of the programmable input and output pins are written into the IORs.
| | | | | | | IOR Byte Defined |
7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |
X | 1 | 0 | X | X | X | X | 0 Disable inputs A and B |
X | 1 | 0 | X | X | X | X | 1 Enable inputs A and B |
X | 1 | 0 | X | X | X | 0 | X LCNTR'/LOL' pin is Load CNTR input |
X | 1 | 0 | X | X | X | 1 | X LCNTR'/LOL' pin is Load OL input |
X | 1 | 0 | X | X | 1 | X | X RCNTR'/ABG pin is Reset CNTR input |
X | 1 | 0 | X | X | 0 | X | X RCNTR'/ABG pin is A and B Enable gate |
X | 1 | 0 | 0 | 0 | X | X | X FLG1 pin is Carry' output, FLG2 pin is Borrow' output |
X | 1 | 0 | 0 | 1 | X | X | X FLG1 pin is Compare' output, FLG2 pin is Borrow' output |
X | 1 | 0 | 1 | 0 | X | X | X FLG1 pin is Carry'/Borrow' output, FLG2 pin is U/D' |
X | 1 | 0 | 1 | 1 | X | X | X FLG1 pin is IDX, FLG2 is E |
0 | 1 | 0 | X | X | X | X | X Select the IOR addressed by X'/Y input |
1 | 1 | 0 | X | X | X | X | X Select both XIOR and YIOR or ZIOR and WIOR together |
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