Rainbow Electronics ATmega103L - Manual (Page 87)

ATmega603/103
87
Port E
Port E is an 8-bit bi-directional I/O port with internal pull-up resistors.
Three I/O memory address locations are allocated for the Port E, one each for the Data Register - PORTE, $03($23), Data
Direction Register - DDRE, $02($22) and the Port E Input Pins - PINE, $01($21). The Port E Input Pins address is read
only, while the Data Register and the Data Direction Register are read/write.
The Port E output buffers can sink 20 mA. As inputs, Port E pins that are externally pulled low will source current if the pull-
up resistors are activated.
All Port E pins have alternate functions as shown in the following table:
When the pins are used for the alternate function the DDRE and PORTE register has to be set according to the alternate
function description.
Port E Data Register - PORTE
Port E Data Direction Register - DDRE
Port E Input Pins Address - PINE
The Port E Input Pins address - PINE - is not a register, and this address enables access to the physical value on each Port
E pin. When reading PORTE, the Port E Data Latch is read, and when reading PINE, the logical values present on the pins
are read.
Table 34. Port E Pins Alternate Functions
Port Pin Alternate Function
PE0 PDI/RXD (Programming Data Input or UART Receive Pin)
PE1 PDO/TXD (Programming Data Output or UART Transmit Pin)
PE2 AC+ (Analog Comparator Positive Input)
PE3 AC- (Analog Comparator Negative Input)
PE4 INT4 (External Interrupt4 Input)
PE5 INT5 (External Interrupt5 Input)
PE6 INT6 (External Interrupt6 Input)
PE7 INT7 (External Interrupt7 Input)
Bit 7 6 5 4 3 2 1 0
$03 ($23) PORTE7 PORTE6 PORTE5 PORTE4 PORTE3 PORTE2 PORTE1 PORTE0 PORTE
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial value 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
$02 ($22) DDE7 DDE6 DDE5 DDE4 DDE3 DDE2 DDE1 DDE0 DDRE
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial value 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
$01 ($21) PINE7 PINE6 PINE5 PINE4 PINE3 PINE2 PINE1 PINE0 PINE
Read/Write R R R R R R R R
Initial value Hi-Z Hi-Z Hi-Z Hi-Z Hi-Z Hi-Z Hi-Z Hi-Z