Address Map; Message Objects - Intel 8XC196K Series User Manual

12.3.1 Address Map

The CAN controller has 256 bytes of RAM, containing 15 message objects and control and status
registers at fixed addresses. Each message object occupies 15 consecutive bytes beginning at a
base address that is a multiple of 16 bytes. The byte above each message object is reserved (indi-
cated by a dash (—) ) or occupied by a control register. The lowest 16 bytes of RAM contain the
remaining control and status registers (Table 12-3). This 256-byte section of memory can be win-
dowed for register-direct access (see "Windowing" on page 4-13).
Hex Address
1EFF —
1EF0–1EFE Message Object 15
1EEF —
1EE0–1EEE Message Object 14
1EDF —
1ED0–1EDE Message Object 13
1ECF —
1EC0–1ECE Message Object 12
1EBF —
1EB0–1EBE Message Object 11
1EAF —
1EA0–1EAE Message Object 10
1E9F —
1E90–1E9E Message Object 9
1E8F —
1E80–1E8E Message Object 8
1E7F —
1E70–1E7E Message Object 7
†
The control register's CCE bit must be set to enable write access to the bit timing registers.

12.3.2 Message Objects

The CAN controller includes 15 message objects, each of which occupies 15 bytes of RAM (Ta-
ble 12-4). Message objects 1–14 can be configured to either transmit or receive messages, while
message object 15 can only receive messages. Message objects 1–14 have only a single buffer,
so if a second message is received before the CPU reads the first, the first message is overwritten.
Message object 15 has two alternating buffers, so it can receive a second message while the first
is being processed. However, if a third message is received while the CPU is reading the first, the
second message is overwritten.
CAN SERIAL COMMUNICATIONS CONTROLLER
Table 12-3. CAN Controller Address Map
Description Hex Address
1E6F —
1E60–1E6E Message Object 6
1E5F Interrupt Register
1E50–1E5E Message Object 5
1E4F Bit Timing Register 1
1E40–1E4E Message Object 4
1E3F Bit Timing Register 0
1E30–1E3E Message Object 3
1E2F —
1E20–1E2E Message Object 2
1E1F —
1E10–1E1E Message Object 1
1E0C–1E0F Message 15 Mask Register
1E08–1E0B Extended Global Mask Register
1E06–1E07 Standard Global Mask Register
1E02–1E05 —
1E01 Status Register
1E00 Control Register
Description
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†
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12-5