Datasheet

311
XMEGA B [DATASHEET]
8291B–AVR–01/2013
25.4.12 Segment and Common Buses Swapping
(1)
Segment and/or common buses can be swapped (mirrored) to give more flexibility for LCD interconnects. The first
segment (or common) terminal pin becomes the last one, and so on.
It is very useful in Chip on Glass (CoG), Chip on Film (CoF) or Chip on Board (CoB) technologies.
SEGSWP bit and COMSWP bit in the CRTLA register control the order of the respective terminal buses.
Note: 1. Refer to specific device datasheet for availability of this feature.
25.4.13 Port Mask
For LCD panels that do not use all the available segment terminals of the device, it is possible to mask some of the
unused pins. PMSK bit-field in the CTRLC register defines the number of segment terminals used in the application. Up
to 16 unused segment terminal pins can be used as standard GPIO pins. They are always placed at the end of the
segment terminal bus. The 8 last pins of this bus will become PG[0:7] - Port G - and the following 8 pins will become
PM[0:7] - Port M.
The GPIO functions on LCD pins are enabled if the corresponding segment terminal is masked or if the LCD controller is
disabled. A pure segment terminal - not shared with GPIO - is grounded via a pull-down resistor if it is masked or if the
LCD controller is disabled.
Note: SEGSWP bit, which reverses the segment terminal indexing, will be active even if the LCD controller is disabled
(ENABLE bit in the CRTLA register) and will thus also modify the GPIO pin mapping.
Examples of a 40-segment LCD controller:
 If 30 segments are used:
Segment terminals [39:32] = PG[0:7] , Port G (GPIO functions)
Segment terminals [31:30] = PM[0:1] , Port M (GPIO functions)
Segment terminals [29:0] = SEG[29:0] , LCD (LCD functions)
 If 20 segments are used:
Segment terminals [39:32] = PG[0:7] , Port G (GPIO functions)
Segment terminals [31:24] = PM[0:7] , Port M (GPIO functions)
Segment terminals [23:20] = GND (pull down)
Segment terminals [19:0] = SEG[19:0] , LCD (LCD functions)