Maxim Integrated High-Speed Microcontroller Users Guide: Network Microcontroller Supplement - Manual (Page 116)

High-Speed Microcontroller User’s
Guide: Network Microcontroller
Supplement
116
ADDENDUM TO SECTION 10: PARALLEL I/O
Changes to this section primarily involve the additional functionality associated with ports 4–7.
Port 0
Port 0 cannot be used for general-purpose I/O, hence no directly addressable SFR is provided for P0. The traditional P0 SFR address
(80h) has been assigned to port 4.
Ports 4–7
Ports 4–7 are general-purpose I/O ports with optional special functions associated with each pin. Enabling the special function auto-
matically converts the I/O pin to that function. To ensure proper operation, each alternate function pin should be programmed to a logic
1. The alternate functions for each port pin are listed as follows:
Port Pin Alternate Function Port Pin Alternate Function
P4.7 A19–Address 19 P6.7 TXD2–Serial port 2 TXD
P4.6 A18–Address 18 P6.6 RXD2–Serial port 2 RXD
P4.5 A17–Address 17 P6.5 A21–Address 21
P4.4 A16–Address 16 P6.4 A20–Address 20
P4.3 CE3–Chip enable 3 P6.3 CE7–Chip enable 7
P4.2 CE2–Chip enable 2 P6.2 CE6–Chip enable 6
P4.1 CE1–Chip enable 1 P6.1 CE5–Chip enable 5
P4.0 CE0–Chip enable 0 P6.0 CE4–Chip enable 4
P5.7 PCE3–Peripheral chip enable 3 P7.7 A7–Address 7
P5.6 PCE2–Peripheral chip enable 2 P7.6 A6–Address 6
P5.5 PCE1–Peripheral chip enable 1 P7.5 A5–Address 5
P5.4 PCE0–Peripheral chip enable 0 P7.4 A4–Address 4
P5.3 —— None —— P7.3 A3–Address 3
P5.2 T3–Timer/counter 3 input P7.2 A2–Address 2
P5.1 C0RX–CAN receive input P7.1 A1–Address 1
P5.0 C0TX–CAN transmit output P7.0 A0–Address 0
General-Purpose I/O
All of the above port pins (P4–P7) can serve as a general-purpose I/O. Data written to the port latch serves to set both level and direc-
tion of the data on the pin. Details on the function of port pins, when configured as general-purpose I/O, are provided in the High-Speed
Microcontroller User’s Guide. The DC electrical specifications for these pins, when used as I/O, can be found in the DS80C400 data
sheet.
Alternate Functions A0–A7, A16–A21, CE0–CE7, and PCE0–PCE3
When any P4, P5, P6, or P7 pin is configured in its alternate function, and that function concerns memory interfacing (A0–A7, A16–A21,
PCE0–3 or CE0–7), the pin is driven using the stronger memory interface values (I
OL2
, I
OH3
), as shown in the DC Electrical
Characteristics section of the DS80C400 data sheet.
Current-Limited Transitions
The DS80C400 does not employ the current-limited transition feature described in the High-Speed Microcontroller User’s Guide.
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